Dell Compellent Storage Center - MicrosoftMultipath I/O Best Practices Kris Piepho, Microsoft Product Specialist January 2015 Dell Best Practices Revisions Date Description 10/11/2010 Initial release 10/21/2011 Corrected Errors 11/29/2011 Additional content on Server Core 10/15/2012 Updated to include Windows Server 2012 content 5/29/2013 Updated to include Server 2008 R2/2012 iSCSI initiator setup and appendix listing recommended hotfixes and registry values 10/18/2013 Updated to include Windows Server 2012 R2 content 1/10/2014 Updated hotfix information 1/12/2015 Updated configuration recommendations THIS WHITE PAPER IS FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND. © 2015 Dell Inc. All rights reserved. Reproduction of this material in any manner whatsoever without the express written permission of Dell Inc. is strictly forbidden. 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Dell disclaims any proprietary interest in the marks and names of others. 2 Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices | CML1004 Table of contents Revisions ..................................................................................................................................................................................................2 1 2 Preface ..............................................................................................................................................................................................5 1.1 Audience................................................................................................................................................................................5 1.2 Purpose ..................................................................................................................................................................................5 1.3 Disclaimer .............................................................................................................................................................................5 1.4 Customer support ...............................................................................................................................................................5 Introduction to Microsoft Multipath I/O .................................................................................................................................. 6 2.1 Multipath I/O overview...................................................................................................................................................... 6 2.2 Dell Compellent Storage Center connections ............................................................................................................ 6 2.2.1 Legacy ports ........................................................................................................................................................................ 6 2.2.2 Virtual ports........................................................................................................................................................................... 7 2.2.3 Conclusion ........................................................................................................................................................................... 8 3 Configuring servers ....................................................................................................................................................................... 9 3.1.1 Fibre Channel ...................................................................................................................................................................... 9 3.1.2 iSCSI....................................................................................................................................................................................... 9 4 3.2 Automatic configuration ................................................................................................................................................. 10 3.3 Manual configuration ....................................................................................................................................................... 11 3.4 Verifying connectivity ....................................................................................................................................................... 11 3.5 Choose the I/O transport ................................................................................................................................................14 MPIO for Windows Server 2003................................................................................................................................................ 15 4.1 Dell Compellent Multipath Manager ............................................................................................................................. 15 4.2 Configuration .....................................................................................................................................................................16 4.3 Choosing a failover policy ...............................................................................................................................................16 4.4 iSCSI multipath options .................................................................................................................................................... 17 4.4.1 Installing the Microsoft iSCSI DSM ................................................................................................................................ 17 5 4.5 Configuring the iSCSI Initiator ....................................................................................................................................... 18 4.6 Configuring Microsoft iSCSI DSM ................................................................................................................................. 20 Using MPIO on Windows Server 2008 and 2008 R2 .......................................................................................................... 23 5.1 Installing the Microsoft MPIO DSM .............................................................................................................................. 23 5.1.1 Server manager GUI......................................................................................................................................................... 23 5.1.2 Server manager CLI (2008 and 2008 R2 only) .......................................................................................................... 23 3 Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices | CML1004 5.1.3 To install MPIO on Server Core: .................................................................................................................................... 23 5.2 Associating Dell Compellent volumes with the DSM ............................................................................................... 24 5.3 Setting the default load balance policy ....................................................................................................................... 25 5.3.1 Windows Server 2008 default load balance policy .................................................................................................. 25 5.3.2 Windows Server 2008 R2 default load balance policy ............................................................................................ 25 5.4 Per-volume load balance settings ................................................................................................................................ 26 5.4.1 Using MPCLAIM in Windows Server 2008 R2, 2012 and 2012 R2 ......................................................................... 27 6 MPIO for Windows Server 2012 and 2012 R2 ....................................................................................................................... 28 6.1 Install the Microsoft MPIO feature ................................................................................................................................ 28 6.1.1 Server manager GUI......................................................................................................................................................... 28 6.1.2 Enable MPIO with PowerShell ....................................................................................................................................... 30 6.2 Associate Dell Compellent volumes with the in-box DSM ..................................................................................... 30 6.2.1 Using the MPIO control panel ........................................................................................................................................ 31 6.2.2 Using PowerShell.............................................................................................................................................................. 33 6.3 Set the Default Load-Balancing Policy ........................................................................................................................ 34 6.4 Per-volume load balance settings ................................................................................................................................ 35 6.4.1 Using the disk management GUI: ................................................................................................................................. 35 6.4.2 Using PowerShell.............................................................................................................................................................. 36 7 Configure a Windows 2008 R2, 2012 and 2012 R2 Server for iSCSI MPIO .................................................................... 38 7.1 4 Configuration .................................................................................................................................................................... 39 A Windows Server MPIO configuration recommendations for Dell Compellent Storage Center ................................ 43 B Additional resources ................................................................................................................................................................... 50 Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices | CML1004 1 Preface 1.1 Audience This document was written for system administrators responsible for the setup and maintenance of Windows® servers and associated storage. Readers should have a working knowledge of Windows and the Dell Compellent™ Storage Center. 1.2 Purpose This document provides an overview of Multipath I/O (MPIO) and introduces best practice guidelines for configuring MPIO on Windows Server® 2003, 2008, 2008 R2, 2012 and 2012 R2 when using the Dell Compellent Storage Center. For installation procedures, download the MPIO Users Guide from http://knowledgecenter.compellent.com. 1.3 Disclaimer The information contained within this document provides general recommendations. Configurations will vary in customer environments due to individual circumstances, budget constraints, service level agreements, applicable industry-specific regulations, and other business needs. 1.4 Customer support Dell Compellent provides live support at 1-866-EZSTORE (866.397.8673), 24 hours a day, 7 days a week, 365 days a year. For additional support, email Dell Compellent at
[email protected]. Dell Compellent responds to emails during normal business hours. 5 Dell Compellent Storage Center - Microsoft Multipath I/O Best Practices | CML1004 servers still need a way to spread the I/O load and handle internal failover from one path to the next. This is where MPIO plays an important role.Microsoft Multipath I/O Best Practices | CML1004 . Dell Compellent provides a DSM for Windows Server 2003. Even more ports are required for a dual fabric. this requires twice as many I/O ports to enable multiple paths. The MPIO framework uses Device Specific Modules (DSM) to allow path configuration. In terms of MPIO.2 Dell Compellent Storage Center connections Before reviewing server-specific MPIO functions. Primary/reserved ports allow I/O to use the primary path. 6 Dell Compellent Storage Center . the reserve port is in a standby mode until a primary port fails over to the reserve port. 2.1 Multipath I/O overview Microsoft® MPIO is a framework that allows administrators to configure load balancing and failover processes for Fibre Channel and iSCSI connected storage devices. Currently there are two options available: Microsoft provides a built-in generic Microsoft DSM (MSDSM) for Windows Server 2008 and above. This MSDSM provides adequate functionality for Dell Compellent customers.com 2. servers see multiple instances of the same disk device in Disk Management. The following section provides a quick overview and explains the differences between legacy port mode and virtual port mode. Figure 1 illustrates dual-fabric failover ports in legacy mode. Without MPIO. Load balancing can be configured to use up to 32 independent paths from the connected storage devices. However. Dell Compellent Storage Centers provide redundancy and failover with multiple controllers and RAID modes.2 Introduction to Microsoft Multipath I/O 2. it is important to understand that various connection options are available with the Dell Compellent Storage Center which allows multiple paths to be presented to the servers.compellent.2. This overview does not take the place of the Storage Center Connectivity Guide available on http://kc.1 Legacy ports In legacy mode. the front-end I/O ports are designated as either primary or reserve ports based on a fault domain. and the reserved port in that fault domain connects to the other controller.2. Figure 2 7 Virtual Port Configuration Dell Compellent Storage Center .0. Dell Compellent implemented virtual ports.2 Virtual ports Dell Compellent introduced virtual port mode with Storage Center 5. For redundancy. For this reason. All front-end I/O ports can be used at the same time for load balancing as well as failover to another port. Fibre Channel To use virtual ports for Fibre Channel. Virtual ports allow all front-end I/O ports to be virtualized.Figure 1 Legacy primary/reserve configuration Figure 1 shows four fault domains connected to a Series 40 Dell Compellent Storage Center with two controller heads. Virtual ports are available for Fibre Channel connections only. or both Fibre Channel and iSCSI. 2. it requires a large number of ports. While this is a highly robust failover solution. all Fibre Channel switches and HBAs must support N_Port ID Virtualization (NPIV).Microsoft Multipath I/O Best Practices | CML1004 . Each fault domain has a primary and reserved port. a primary port connects to one controller. iSCSI connections only. Failover with this configuration uses half the ports and is just as robust as the one shown in Figure 1. iSCSI only.Figure 2 shows a virtual port configuration. this looks slightly different than with the legacy mode configuration because only the control port in the iSCSI Initiator software needs to be assigned. If one port fails. iSCSI iSCSI follows the same wiring and port setup as Fibre Channel with the exception of the control port. All ports are active. or both. Servers connect to the control port. These differences are covered below in the OS-specific sections of this document. iSCSI uses a control port configured for each of the fault domains.3 Conclusion There are two methods to enable multiple paths from the Dell Compellent Storage Center: legacy port mode and virtual port mode. the load is distributed between remaining ports. Note that virtual ports are enabled based on protocol: virtual ports can be enabled on Fibre Channel only. All ports of one transport type (Fibre Channel or iSCSI) are in the same fault domain.Microsoft Multipath I/O Best Practices | CML1004 . 8 Dell Compellent Storage Center .2. 2. When configuring MPIO. Virtual ports are preferred because they reduce the number of HBAs required and thus reduce cost and overhead. which then redirects traffic to the appropriate virtual port. iSCSI virtual ports connect only to a control port on the Storage Center. This is covered in more detail in the OS specific sections. an iSCSI server can be created automatically or manually. Use either the HBA BIOS or the Software Initiator configuration wizard. with legacy ports. The following example assumes a server has two or more Fibre Channel or iSCSI I/O ports that are zoned or VLAN’d to see the Storage Center host bus adapters (HBAs).Microsoft Multipath I/O Best Practices | CML1004 . creating a server in the Storage Center is the same on all operating systems. the server cannot see reserve ports. enter the IP address of the control port. the process is the same for virtual ports as it is for legacy ports. With Fibre Channel. 3. The easiest way to do this is to boot the server into the card's BIOS and scan the SCSI devices on each port. properly zone the switches so that the server and controller ports are in the same zone.1. For automatic configuration. 3. However.2 iSCSI As with Fibre Channel. enter the IP address of the Storage Center controller HBA ports in the server iSCSI HBA or Initiator Software. However.1 Fibre Channel To create the server. An alternate method is to preconfigure the WWNs of the HBAs in the Storage Center System Manager. In legacy port mode. first configure servers using the Dell Compellent System Manager.3 Configuring servers Before configuring MPIO at the operating system level. enter the IP address of the primary port.1. 9 Dell Compellent Storage Center . In virtual port mode. 3. Select the appropriate HBAs and continue the wizard. Log in to the Dell Compellent System Manager. refer to Section 3. In the tree view. 2.Microsoft Multipath I/O Best Practices | CML1004 . 4.2 Automatic configuration Once a server has scanned for devices or logged into the target. right-click on Servers. Note: If the WWN or IQN is not listed.3. 3. Manual configuration. make sure that the Only Show Up Connections box is not checked. Storage Center automatically recognizes the WWN/IQN. To configure a server: 1. If the HBA does not appear. Figure 3 10 Create Server window Dell Compellent Storage Center . select Create Server. From the shortcut menu. 2.3 Manual configuration To manually configure an HBA: 1. choose Fibre Channel or iSCSI. 3. 4. Note: The new HBA appears with a white X in a red circle. Once the server is connected the warning state is removed.4 Manually defined HBA Verifying connectivity To verify that the connectivity is correct: 1. Repeat steps 1-3 for every WWN or iSCSI HBA to be associated with the server. In the Create Server wizard shown in Figure 3. 11 Dell Compellent Storage Center . 2. In the Select Transport Type window.3. Click Connectivity. check the appropriate HBA and continue the wizard. and click Continue. In the tree view. Enter the WWN or iSCSI name. click Manually Define HBA. Once all HBAs are added.Microsoft Multipath I/O Best Practices | CML1004 . Figure 4 3. select a server. This window shows all paths available to the server based on the HBA and controller ports. For Fibre Channel there are four possible paths because two HBAs see two Storage Center ports. -or. Click Advanced. a volume is mapped to all available paths unless the advanced mapping button is used to restrict mapping paths to FC only. Check Only map using specified server ports. 3. To restrict mapping paths: 1. right-click a volume and select Map Volume to Server. Select a server and click Continue. Select a transport from the drop-down menu.Microsoft Multipath I/O Best Practices | CML1004 . 5. The Map Volume to Server window appears. Select one of the following: . iSCSI only. 12 In the tree view. or specified HBA ports and controller ports. However. the server has visibility to a total of 10 paths to a volume.Figure 5 Connectivity tab The connectivity tab displays the HBAs and controller ports that the server can see. there are a total of six connections where there are two separate IP addresses going to three Storage Center ports. for iSCSI. The Map Volume window appears.Map using specific server ports. In Storage Center. 4. 2.Limit ports by transport type. Dell Compellent Storage Center . If MPIO is not installed and the volume is mapped using the default mapping method. Check the specific server ports. Figure 7 Volume Mapping tab Figure 7 shows that MPIO Volume 1 was mapped to the server with four FC ports and two iSCSI ports. select a volume in the tree view and click the Mapping tab.Microsoft Multipath I/O Best Practices | CML1004 .Figure 6 Advanced Mapping wizard Assuming the default mapping wizard is used and paths are not restricted. 13 Dell Compellent Storage Center . a volume is mapped to all available paths. creating multiple I/O paths from the server to the volume. To view the mapped paths. 3. The remainder of this document focuses on specific MPIO configuration options available from: Windows Server 2003 Dell Compellent-provided DSM Windows Server 2008 and above MSDSM Microsoft iSCSI DSM It is assumed that there are multiple front-end controller paths to the servers and that the servers have multiple connections to the controller.5 Choose the I/O transport Most organizations today have settled on either Fibre Channel or iSCSI for the I/O transport mechanism. Choosing between these two depends on what the organization has in place today and where they are heading in the future. For a converged fabric iSCSI is the best option because it can utilize existing networking infrastructure.Microsoft Multipath I/O Best Practices | CML1004 . Dell Compellent offers 8GB and 16GB Fibre Channel and 10GB iSCSI. With the advent of 10GB iSCSI. 14 Dell Compellent Storage Center . the performance gap between these two transports has narrowed. You can configure the failover only policy to behave as failback by setting the active path and enabling the preferred path option. this can be changed to round robin or round robin subset. Allows multiple active and standby paths. configure the load balance policies for the volumes attached to the server. This chapter describes each of these options and provides guidance on how to configure MPIO with both the Storage Center DSM and the Microsoft DSM. For failback. The default load balance policy for the Dell Compellent DSM is failover-only. 4. iSCSI can be configured with either the Microsoft iSCSI DSM or the Dell Compellent Multipath Manager. I/O fails over to the next available standby path only when the active path fails.Microsoft Multipath I/O Best Practices | CML1004 . For information on installing and configuring the Dell Compellent Multipath Manager. the first discovered path is the active path. Failover only: Only one path is active. 15 Dell Compellent Storage Center . the system fails back to the original active path when it becomes available after a failover. I/O is distributed across all active paths. Round robin subset.4 MPIO for Windows Server 2003 Windows Server 2003 offers two methods for handling MPIO: Storage Center ISV-provided DSM Microsoft iSCSI DSM These two methods cannot be used concurrently in the Windows 2003 platform. The round robin subset policy can be configured to behave as failback by explicitly setting one or more active paths. However. refer to the Storage Center Multipath I/O (MPIO) Manager for Microsoft Servers User Guide on the Dell Compellent Knowledge Center. Round robin: All paths are active and I/O is distributed across all paths. The new active path remains active until another failover occurs.1 Dell Compellent Multipath Manager The Dell Compellent Multipath Manager is a Dell Compellent-provided DSM that handles all Fibre Channel and iSCSI failover and load balancing. Once the Dell Compellent DSM has been installed. the system fails back to the original active path when it becomes available after a failover. Standby paths are used only when all active paths fail. Fibre Channel requires the Dell Compellent Multipath Manager. For failback. By default. Note: If moving to a round robin policy. 4. 16 Dell Compellent Storage Center . Also. Below is a brief overview of how to change the policies. resulting in underutilized resources in a data center. it may not provide adequate bandwidth for certain workloads. To change the policy for a given device: 1. failover is required in most organizations. any I/O ports in standby mode are sitting idle until a failover occurs. 2.2 Configuration To configure the default load balance policy or to change the active configuration of the DSM. notice that the device paths do not change from standby to active until the settings are applied and the wizard is restarted or refreshed. performance. However. select a policy for the environment. Click Set Default Policy at the top of the screen. select the desired load balance policy. 2.3 Choosing a failover policy Determining the best failover policy is accomplished by deciding which is more important for the application: failover. open the Dell Compellent Multipath Manager Configuration wizard from the Program Files menu. Click on the device. To change the default load balance policy for all future volumes attached to the system: 1. As mentioned previously in failover only mode.4. the server uses only one path at a time. in today's world of zero downtime.Microsoft Multipath I/O Best Practices | CML1004 . While this ensures redundancy. From the drop down menu. or a combination of both. In the Policy field. Cost also plays a significant role in the decision since having multiple paths adds to the overall cost of a solution. if the built-in Microsoft iSCSI DSM is installed. the system uses the remaining paths to complete the request.Microsoft Multipath I/O Best Practices | CML1004 .4 iSCSI multipath options As mentioned previously. In the Dell Compellent Configuration window.1 Installing the Microsoft iSCSI DSM To install the MS iSCSI DSM. Otherwise there is no way to control the Fibre Channel MPIO functionality. on the other hand. Typically this is done for a server with volumes connected only via the iSCSI transport. simply install the iSCSI initiator software and select Microsoft MPIO Multipathing Support for iSCSI. the Dell Compellent Multipath Manager handles both FC and iSCSI connections.4. the best practice is to use the Dell Compellent DSM and not install the Microsoft iSCSI DSM. If a Windows Server 2003 is using both transports.Round robin. provides a means for I/O to traverse all available paths while still providing a level of redundancy. Figure 8 Dell Compellent DSM with both FC and iSCSI However. 4. the Dell Compellent Multipath Manager software must be uninstalled. 4. the transport for each connection can be viewed and configured for each volume. If one path fails. 17 Dell Compellent Storage Center . 5 Configuring the iSCSI Initiator When using the MS DSM or the Dell Compellent DSM for iSCSI. Before jumping into MPIO configuration with iSCSI it is important to understand how to connect and configure the iSCSI initiator. In the following examples. the server is configured with two NIC cards. 18 Dell Compellent Storage Center . Click the Discovery tab. all iSCSI volume MPIO characteristics are controlled by the MS iSCSI DSM. It assumes that the initiator software is installed. each used to communicate with the iSCSI network. The Discovery tab contains two sections: Target Portals and iSNS Servers. Dell Compellent front-end ports are added as target portals.Figure 9 Installing MS iSCSI DSM Once installed.Microsoft Multipath I/O Best Practices | CML1004 . and the Dell Compellent Storage Center has two or more iSCSI front-end ports. 4. Open the iSCSI Initiator. To configure the connection to the Dell Compellent Storage Center: 1. 2. This section describes how to configure the iSCSI Initiator and make this connection. the server must first be configured to communicate with the Dell Compellent iSCSI front-end ports. the server has been rebooted. Check Automatically Restore to reconnect after a reboot. Follow the steps below to make a connection for each. Click Add. Each IP address is logged in to each target. Click the Targets tab. Enter any Chap login information and click OK. 11. Dell Compellent Storage Center . each of the NIC cards must be logged in to each target. 10.3. 5. In this example there are two targets. thus providing multiple connections to a specific target. Create a server (if it hasn't already been created). it is entered two times for each target. 9. 7. For MPIO to function correctly. Select the Target Portal. Select the same target and click Log On again. This log-on sequence must be done for each IP address that communicates with the front-end port. 13. 4. enter the IP address of the control port. Select Microsoft iSCSI Initiator from the Local adapter drop-down box. If using legacy port mode. If using virtual port mode. 12. Select the necessary checkboxes for Data Digest and Header Digest. Do not enter reserve ports. creating four separate connections to the controller. 15. 19 Open the Dell Compellent System Manager. Check Enable multi-path. Select the first target and click Log On. 8. enter the first primary port IP address. there are two targets and two source IP addresses. Click Advanced.Microsoft Multipath I/O Best Practices | CML1004 . 6. In this example. 14. The advanced options window is where each NIC card is selected to connect to the target. To verify: 1. Continue until all frontend ports have been added. Select the first IP address from the Source IP. In this example. Repeat steps 3-11 for each Source IP and each additional target. 2. Select each target and click Details. 4. Click the Connectivity tab. Click the server in the tree view. Within the details section. The iSCSI Initiator provides another method for verification: 1.5.5.25. The connectivity window shows the IQN of the server and associated controller ports (target IP addresses) that the server can see. 3. From the Targets tab in the iSCSI Initiator.2. 20 Dell Compellent Storage Center .25.33 and 10. 2. Click Connections to verify that each connection is using a different source IP address. the two Dell Compellent ports see each of the server IP addresses as being connected (10. As seen in this example. The next step is to use the Microsoft iSCSI DSM to configure the default load balance policy for any new volumes that are mapped to the server. select each of the targets. there are two or more Identifiers. 3. To configure the default MPIO policy: 1. Open the iSCSI Initiator and click the Targets tab.6 Configuring Microsoft iSCSI DSM At this point the server and the Dell Compellent Storage Center are connected and the connectivity has been verified.40). Click Details to see that there are two connections for each of the targets.Microsoft Multipath I/O Best Practices | CML1004 . To configure the MPIO policy for pre-existing volumes: 1. In the Advanced window click MPIO. For each device.3. 6. Dell Compellent Storage Center . Using the drop down menu. 2. and click Apply. click Advanced.Microsoft Multipath I/O Best Practices | CML1004 . Select the appropriate policy for each volume and then click Apply. Select each target individually. 4. 4. Note that this must be done for each connection. Select each one and click Connections. Click Details and then Devices. select an appropriate load balance policy for that connection. 21 Open the iSCSI Initiator and click Targets. 3. 5. The weight indicates the relative priority of a given path. the lower the priority. Weighted Paths: A weight is assigned to each path. the Dell Compellent Multipath Manager Software must be used.Microsoft Multipath I/O Best Practices | CML1004 . 22 Dell Compellent Storage Center . Note: Dell Compellent Storage Center does not support the three additional policies provided by the Microsoft iSCSI DSM. However. In conclusion. If multiple protocols are in use on the server.The Microsoft iSCSI DSM offers three additional policies that are not provided by the Dell Compellent DSM. Note: Remember that both DSMs cannot be used on the same server because this will cause issues with the MPIO stack. The larger the number. Least Blocks: The DSM routes requests to the processing path with the least number of pending I/O blocks. if iSCSI is the only transport. Least Queue Depth: The DSM routes I/O to the path with the least number of outstanding requests. there are two methods for handling MPIO in the Windows Server 2003 operating system. The DSM chooses the path with the least weight. the Microsoft iSCSI DSM is a valid choice. 4. open a command prompt and type: start ocsetup MultipathIo 23 Dell Compellent Storage Center . The built-in DSM for Windows Server 2008 (and above) can manage both iSCSI and FC volumes.1 Installing the Microsoft MPIO DSM For Windows Server 2008 and above. The process for mapping volumes and creating servers is identical to the process with Windows Server 2003 described in Section 3. There are currently two available options for installing the DSM: the Server Manager GUI or the servermanagercmd command line interface (CLI). 5. to allow the reboot.1. 5. 2.1. Click Install. A new configuration tool. Dell Compellent uses this DSM because it provides all the functionality required for our customers. provides a single interface for installing server features and roles. open a command prompt with elevated (administrator) privileges and type: Servermanagercmd -install "Multipath-IO" 5. The rest of Section 5 covers Windows Server 2008 and 2008 R2 configuration options. Check MPIO and click Next. Note: Please refer to Appendix A in this document for important Windows Server 2008 and 2008 R2 MPIO configuration recommendations. 5. 3. click Features.1.1 Server manager GUI To install using the GUI on Server 2008 and 2008 R2: 1.Microsoft Multipath I/O Best Practices | CML1004 . This also simplifies implementation. In the tree view. Once the feature has been installed click Yes.2 Open Server Manager. “Configuring servers”.3 To install MPIO on Server Core: For a Windows Server 2008 Core installation. as it eliminates the need to install and maintain another piece of software in the environment. the Server Manager.5 Using MPIO on Windows Server 2008 and 2008 R2 Windows Server 2008 and 2008 R2 have a built-in Microsoft DSM that manages all aspects of failover and load balancing. the process of installing and configuring the Microsoft MPIO DSM has been streamlined. To access Server Manager click Start Control Panel Administrative Tools Server Manager or click the Server Manager icon in the toolbar. if prompted. Server manager CLI (2008 and 2008 R2 only) To install using the CLI. Open the MPIO control panel by clicking Start Administrative Tools MPIO. This can take a minute.2 Associating Dell Compellent volumes with the DSM This section will describe how to associate the DSM with Dell Compellent volumes and how to setup and configure the DSM based on the failover and load balancing policies of an organization. These instructions assume that servers have been created in the Dell Compellent System Manager and that at least one volume is mapped to the server via FC or iSCSI with MPIO enabled. It associates a Dell Compellent volume and then restarts the server. At this point. Dell Compellent supports use of an HBA. The Microsoft DSM manages all Fibre Channel and iSCSI volumes presented by the Dell Compellent Storage Center. open a command prompt and type: DISM /online /enable-feature:MultipathIo Note: For server core installations. use Disk Management to verify that the configuration is correct. COMPELNTCompellent Vol appears. Another option for providing associations is the MPCLAIM CLI command. rescan disk devices in Disk Management. Once the server reboots. However. Click on COMPELNTCompellent Vol and then click Add. Open a command prompt with elevated (administrator) privileges and type the following: mpclaim. The iSCSI initiator provides all necessary performance and stability. use -n in place of the -r. Once opened. To associate the DSM with Dell Compellent volumes: 1. 2.Microsoft Multipath I/O Best Practices | CML1004 . the above commands are case sensitive and must be run before the MPCLAIM command can be used. click Discover Multi-Paths. When Disk Management prompts to reboot the server. The built-in iSCSI initiator or an iSCSI HBA can also be used with the same management for the iSCSI Multipath I/O. 5. You can choose either or both of these transports. This reboot is required to set up the association between the volumes and the DSM. There should only be one instance of each SAN volume listed in Disk Management. 3. 24 Dell Compellent Storage Center . accept the prompt and allow the server to reboot.For a Window Server 2008 R2 Core installation. Note: If COMPELNTCompellent Vol does not appear. Under Others.exe -r -i -d "COMPELNTCompellent Vol" This command provides the same result as the Control Panel option. To bypass the reboot option (if rebooting later is desired). Dell Compellent volumes must be associated with the DSM so that it can manage MPIO characteristics. the Microsoft MPIO DSM has been installed but not configured. To change the default load balance policy in Server 2008 R2.3.exe -L -M 1 -d "COMPELNTCompellent Vol" Note: Failover Only and Round Robin are the only policies supported on Dell Compellent Storage Center. 25 Dell Compellent Storage Center . There are some slight differences between Windows 2008 and Windows 2008 R2. 2008 R2 and newer provides a method for changing the default policy system-wide as well as on a per-volume basis.Microsoft Multipath I/O Best Practices | CML1004 .exe -L -M <0-7> -d "COMPELNTCompellent Vol" <0-7> refers to the desired load balance policy and shown in Table 1. the Dell Compellent volumes have a load balance policy of failover only because a Storage Center is not an Asymmetric Logical Unit Assignment (ALUA) device. there is no way to change the default policy. a Storage Center is designated as a Round Robin device by default. to change all Dell Compellent volumes to a failover only policy. However. The same procedure is used to change the policy on a per-volume basis with both Windows 2008 and Windows 2008 R2.5. 5. Therefore.3 Setting the default load balance policy Once the volumes are associated. 5.2 Windows Server 2008 R2 default load balance policy With Server 2008 R2 and newer.3. Server 2012 and Server 2012 R2. Table 1 Windows 2008 R2 Load Balance Policy Parameter Definition 0 Clear the policy 1 Failover only 2 Round robin 3 Round robin with subset 4 Least queue depth 5 Weighted paths 6 Least blocks 7 Vendor specific For example. specify the default load balance policy and change any existing volumes to use the new policy. use the following command: mpclaim. use the MPCLAIM CLI command as follows: mpclaim. Unfortunately with Server 2008.1 Windows Server 2008 default load balance policy By default in Windows Server 2008. it is imperative that the policy is changed to reflect the best practices of an organization each time a volume is mapped to the server. 4 Per-volume load balance settings Now that the default policy is set. From the drop-down box.5. select the appropriate MPIO policy for the volume. In the tree view. Click Start Administrative Tools Server Manager. Right-click the disk number in the disk column and select Properties. Some organizations may require a different policy based on the type of application or service provided. To change the policy in Disk Management: 1. 26 Dell Compellent Storage Center . 3. it is important to understand how to change the policy on a per-volume basis. 2. 4. 5. Use Disk Management in 2008 and 2008 R2 or through the MPCLAIM utility in 2008 R2 to change the per-volume policy.Microsoft Multipath I/O Best Practices | CML1004 . click Storage Disk Management. Select the MPIO tab. exe -s –d Figure 10 List disks with MPCLAIM Figure 10 shows that the current policy for Disk 0 is RR (Round Robin). in this case the administrator chooses which volume to set. 27 Dell Compellent Storage Center .4. mpclaim.exe command to change the policy for this disk. Use the mpclaim. 2012 and 2012 R2 provide an enhanced MPCLAIM utility that allows the policy to be changed on a per-volume basis much like Disk Management.5.exe -L -M 1 -d 0 Refer to Microsoft TechNet for the full MPCLAIM reference guide.1 Using MPCLAIM in Windows Server 2008 R2. List of all MPIO volumes on the system with the following mpclaim command: mpclaim.Microsoft Multipath I/O Best Practices | CML1004 . The command is similar to setting the default policy for all volumes. 2012 and 2012 R2 Windows Server 2008 R2. However. Windows Server 2012 and 2012 R2 contain a built-in Microsoft DSM out of the box that manages all aspects of failover and load balancing. In previous versions of Windows Server. Note: On Server Core installations. Dell Compellent Storage Center . 6. 6.1 Server manager GUI 1. 28 Open Server Manager. Microsoft recommends using the MPIO module in PowerShell. However. Although the MPCLAIM command is included in Server 2012/R2.6 MPIO for Windows Server 2012 and 2012 R2 MPIO for Windows Server 2012 and 2012 R2 functions the same way as it does for 2008 R2. This chapter focuses on using the GUI and PowerShell to install and configure MPIO. Note: Please refer to Appendix A in this document for important Windows Server 2012 and 2012 R2 MPIO configuration recommendations. it was a requirement to use HBAs of the same model. Server 2012/R2 includes the MPIO module in Windows PowerShell®. Like Windows Server 2008 and 2008 R2.Microsoft Multipath I/O Best Practices | CML1004 . The MPIO module is a powerful alternative to using the MPCLAIM command. Windows Server 2012 and 2012 R2 include the ability to use heterogeneous HBA types with MPIO.1. please follow the instructions for PowerShell.1 Install the Microsoft MPIO feature The MPIO DSM can be installed on Server 2012 and 2012 R2 either through the GUI or through the MPIO module in PowerShell. PowerShell can be accessed on a Server Core installation by typing powershell and pressing [Enter] at the command prompt. and click Next. click Next. 6. From the Dashboard. 7. click Next on the Select server roles screen. and then click Next. Choose the local server. Check Multipath I/O.Microsoft Multipath I/O Best Practices | CML1004 . 29 Dell Compellent Storage Center . Select Role-based or feature-based installation and click Next. 5. 3. 4. click Add roles and features.2. Without selecting a role to install. When the Add Roles and Features Wizard window opens. 8.2 Enable MPIO with PowerShell 1. 9. 6. Click Close when finished. 10. type in the following command: Enable-WindowsOptionalFeature –online –FeatureName MultiPathIO Figure 11 6. Dell Compellent 30 Dell Compellent Storage Center . At the PowerShell prompt. On Windows Server 2012 and 2012 R2. 2.1. Click Install.Microsoft Multipath I/O Best Practices | CML1004 .2 Enable MPIO in PowerShell Associate Dell Compellent volumes with the in-box DSM Now that the DSM has been installed. Check the box to Restart the destination server automatically if required. Open a PowerShell window with elevated (administrator) privileges. Dell Compellent volumes must be associated with the DSM so that the DSM can manage MPIO characteristics. COMPELNTCompellent Vol should be displayed.1 Using the MPIO control panel To associate the Dell Compellent volumes with the DSM through the use of the MPIO Control Panel. Open the MPIO Control Panel through Server Manager. 6. 3. 2. Under Others. Note: Once the DSM is associated with Dell Compellent volumes. or through PowerShell. Windows will automatically claim all Fibre Channel and iSCSI volumes presented from Storage Center and apply default MPIO settings to those volumes.2. Click on the Discover Multi-Paths tab. MPIO can also be accessed through the Control Panel. by clicking Tools and then MPIO. follow these steps.Microsoft Multipath I/O Best Practices | CML1004 . 31 Dell Compellent Storage Center . 1.volumes can be associated with the DSM through the use of either the MPIO Control Panel. 5.4. Click Yes on the Reboot Required window. 6. and click Add. Highlight COMPLENTCompellent Vol.Microsoft Multipath I/O Best Practices | CML1004 . open up the MPIO Control Panel and verify that COMPELNTCompellent Vol is listed under Devices on the MPIO Devices tab. 32 Dell Compellent Storage Center . Once the server has rebooted. 7.On Server Core installations. claim all available Dell Compellent volumes to be used by MPIO by typing: Update-MPIOClaimedHW –Confirm:$false 4. At the PowerShell prompt type: New-MSDSMSupportedHW –VendorID COMPELNT –ProductID ‘Compellent Vol’ 3.Microsoft Multipath I/O Best Practices | CML1004 . Open a PowerShell window with elevated (administrator) privileges. . Using PowerShell To associate the Dell Compellent volumes with the DSM through the use of PowerShell.2 Click OK to close the window. Now that Dell Compellent is supported through the Microsoft DSM. 1. 6.2. Restart the server by typing: shutdown –r –t 0 [Enter] 33 Dell Compellent Storage Center . follow these steps. type in powershell and press [Enter] at the command prompt 2. 6. the default load balancing policy for Server 2012 and 2012 R2 is round robin. the result will return “RR”: Figure 14 Round robin default load balance policy If the default policy is set to failover only. open a PowerShell window with elevated (administrator) privileges and type: Set-MSDSMGlobalDefaultLoadBalancePolicy –Policy FOO [Enter] Figure 12 Set default load balance policy to failover only To change the default load balancing back to round robin. type: Set-MSDSMGlobalDefaultLoadBalancePolicy –Policy RR [Enter] Figure 13 Set default load balance policy to round robin To verify the default load balance policy. the result will return “FOO”: Figure 15 34 Failover only default load balance policy Dell Compellent Storage Center . However. Storage Center supports the round robin and failover only load-balancing policies for Server 2012 and 2012 R2. type: Get-MSDSMGlobalDefaultLoad BalancePolicy If the default policy is set to round robin. the default load balancing policy can be changed system-wide or on a per-volume basis.3 Set the Default Load-Balancing Policy Similar to Server 2008 R2.Microsoft Multipath I/O Best Practices | CML1004 . To change the default load balancing policy to failover only. or from PowerShell.4 Per-volume load balance settings Changing load balance settings on specific volumes can be done through the Disk Management GUI. 4. 35 Dell Compellent Storage Center . In the tree view.Microsoft Multipath I/O Best Practices | CML1004 . 5. From the drop-down box.6. 3. Right-click the desired disk number and select Properties. click Storage Disk Management. select the appropriate MPIO policy (Failover Only or Round Robin) for the volume.4. Click Start Administrative Tools Computer Management.1 Using the disk management GUI: 1. 6. Select the MPIO tab. 2. 2 Using PowerShell The PowerShell MPIO module does not include cmdlets that can change the default load balancing policy on a specific volume. open a command prompt or PowerShell window with elevated (administrator) privileges (commands will work in both): To list all MPIO volumes on the system. The syntax to change the load balancing policy on a specific volume is: 36 Dell Compellent Storage Center . To change the default load balancing policy on a single volume.Microsoft Multipath I/O Best Practices | CML1004 . Note: The load balancing policy cannot be changed from round robin to failover only using the MPCLAIM command. Similar to Server 2008 R2. MPCLAIM only supports switching from failover only to round robin. the MPCLAIM command must be used to make changes to specific volumes.4.6. type : mpclaim –s –d Figure 16 Listing MPIO volumes Figure 16 shows that the load balancing policy (LB Policy) is set to RR (round robin) for all three volumes. For example.Microsoft Multipath I/O Best Practices | CML1004 . to change the load balancing policy of MPIO disk 2 to round robin.2 for load balancing policies and the associated numbers for the mpclaim command. type: mpclaim –l –d 2 2 [Enter] Figure 17 Set load balancing setting Verify the new settings by typing: mpclaim –s –d Figure 18 37 Verifying MPIO settings Dell Compellent Storage Center .mpclaim –l –d <disk #> <0-7> Refer to Table 1 in section 5.3. 2012 and 2012 R2 support MPIO with the iSCSI software initiator. but is still easy to configure.Microsoft Multipath I/O Best Practices | CML1004 .7 Configure a Windows 2008 R2. 2012 and 2012 R2 Server for iSCSI MPIO Windows Server 2008 R2. Two physical iSCSI ports (one from each controller) are grouped logically as a virtual domain that is assigned a virtual iSCSI IP address. iSCSI initiator software is provided natively by the Windows Server OS. Each virtual domain’s physical ports are connected to two separate iSCSI switches to ensure full path redundancy to the dual iSCSI NICs on the server. Configuring iSCSI to use MPIO requires a few more steps. 38 Dell Compellent Storage Center . Figure 19 iSCSI virtual ports and domains Figure 19 represents a dual-controller Dell Compellent Storage Center that is configured with virtual frontend ports with 2 fault domains. The iSCSI quick connect feature works well for single iSCSI path connectivity. For Server 2012 and 2012 R2. complete the following steps.1 (fault domain 200). start Server Manager. 3. b. click on Tools iSCSI Initiator from the drop-down list. In the example shown in Figure 19. For Server 2008 R2.1 (fault domain 100) and 10. In this example. To configure the Server for iSCSI MPIO.10. Enter the IP address of the first iSCSI target IP.10. Two dedicated NIC ports (one for each fault domain) on the server for iSCSI communications. 10.128.7. 1. 4. and from the Dashboard. the server NICs are assigned with IPs of 10. In this example.95. Note: If receiving a prompt to start the iSCSI service (for Server 2008 R2. a.101 (for fault domain 100). 2. 2012.10. and configure the second NIC to access the other virtual iSCSI domain. the server should be able to ping both of the virtual iSCSI IP addresses associated with the two fault domains on the Dell Compellent Storage Center.101 (for fault domain 200).10. Select the Discovery tab. 39 Dell Compellent Storage Center . or 2012 R2. go to Start Administrative Tools iSCSI Initiator. b. The MPIO feature installed on the server. and then click the Discover Portal button. Once configured.1 Configuration The environment created for this configuration includes (refer to Figure 19): Windows Server 2008 R2. click Yes.Microsoft Multipath I/O Best Practices | CML1004 . A Dell Compellent Storage Center with dual controllers configured with virtual front-end iSCSI ports and two virtual fault domains. Configure two physical NIC ports on the server to use iSCSI. c. and then click Advanced. the virtual iSCSI IP address associated with the first virtual fault domain on the Dell Compellent Storage Center.128. Configure one NIC (along with the necessary cabling and switching configurations) to access one virtual iSCSI domain. Log on to the Windows server and launch the iSCSI Initiator software.95. 2012 or 2012 R2). a. and 10. When completed. 7.10. select the local IP address of the server NIC that is to be associated with the first fault domain (fault domain 100). Click OK.128.5.101). Verify that the target IP address and adapter IP address are displayed in the Target Portals window.10. From the Local adapter drop-down list. and then OK again to return to the iSCSI Initiator properties window.101.95.Microsoft Multipath I/O Best Practices | CML1004 . 40 Dell Compellent Storage Center . 10. 9. 8.128. 6. From the Initiator IP drop-down list. select Microsoft iSCSI Initiator. 10. Repeat steps 3 – 8 to add the second target IP for the second virtual fault domain and the server second iSCSI NIC (in this example. both pairs of iSCSI initiators and targets should be listed. This example uses Initiator IP 10.1 and 10.10. and then click Connect. Highlight the first target.11. This should be populated with the discovered iSCSI target ports on the Dell Compellent Storage Center. 14. On the Connect To Target screen. Select the Targets tab. 41 Dell Compellent Storage Center . 13. 12.Microsoft Multipath I/O Best Practices | CML1004 . verify that both Add this connection to the list of Favorite Targets and Enable multi-path are checked. Click Advanced to display additional options. Microsoft Multipath I/O Best Practices | CML1004 . 19. 18. Click OK to exit the iSCSI Initiator properties window. Repeat steps 12-17 above for each additional target listed. and then OK again to return to the iSCSI Initiator properties window. 16.15. 42 Dell Compellent Storage Center . 17. When finished. Select the correct IP addresses for the Target portal IP and Initiator IP from the drop-down lists. Set Local adapter to Microsoft iSCSI Initiator. all the targets should show as Connected as shown below. 20. Click OK. sys – 7/13/2013) KB2851144 Computer loses track of LUNs after a path http://support.com/kb/2871163 (storport.sys – 3/9/2012) Table 3 Recommended MPIO hotfixes for Windows Server 2012 (non R2 version) KB Number Title Link KB2867201 Stop Error 0x00000050 occurs when new StorPort features are implemented in Windows 8 or Windows Server 2012 http://support.sys – 6/29/2013) KB2889784 43 Windows RT.microsoft.sys – 11/30/12) KB2684681 Iscsicpl.microsoft.sys – 6/1/2013) KB2754704 A hotfix is available that provides a mechanism for DSM to notify MPIO that a particular path is back to online in Windows Server 2008 and Windows Server 2008 R2 http://support.A Windows Server MPIO configuration recommendations for Dell Compellent Storage Center Table 2 Recommended MPIO hotfix for Windows Server 2008 R2/SP1 KB Number Title Link KB2871163 No warning logged when the Storport miniport driver tries to use more than 8 SCSI buses in Windows Server 2008 R2 http://support.microsoft.com/kb/2684681 (msiscsi.com/kb/2754704 (mpio. Windows Server 2008.microsoft.Microsoft Multipath I/O Best Practices | CML1004 .com/kb/2889784 Dell Compellent Storage Center .com/kb/2851144 failover occurs between storage controllers in Windows Server 2008 R2 or Windows Server 2012 (msdsm.com/kb/2867201 (storport. and Windows Server update rollup: November 2013 http://support.microsoft. or Windows Server 2008 R2 http://support. Windows 7.microsoft. Windows 8.exe process stops responding when you try to reconnect a storage device to a computer that is running Windows Vista. (msdsm.com/kb/2869606 (mpio.microsoft.sys – 10/04/2013) KB2869606 The LUN for a storage device is lost when multiple paths are lost concurrently in Windows Server 2012 http://support.sys – 11/6/2012) 44 Dell Compellent Storage Center .Microsoft Multipath I/O Best Practices | CML1004 .microsoft.com/kb/2779768 (msiscsi.sys – 10/12/2013) KB2779768 Windows 8 and Windows Server 2012 update rollup: December 2012 http://support. Dell Compellent Storage Center . it is disabled. and the failure is exposed to the application rather than attempting to continue to recover active paths. the recommended value of 90 seconds will be sufficient. 0 1 PathVerifyEnabled 0 no change This flag enables path verification by MPIO on all paths every N seconds (where N depends on the value set in PathVerificationPeriod). a value of 60 can be used. and 2012 R2. In environments with failover clusters that require faster failover times. System administrators are advised to test settings on a non-production environment to make informed decisions on setting timeout values. 2012.Note: All recommended registry settings apply to Windows Server 2008 R2. Note: The maximum time allowed for Storage Center controller failover is 60 seconds. 20 120 PathRecoveryInterval Represents the period after which PathRecovery is attempted. pending I/O operations will be failed. even after losing all paths to the device. The value of PDORemovePeriod directly correlates to this value. it allows the use of PathRecoveryInterval. By default. This Boolean function must be filled with either 0 (disable) or 1 (enable). Table 4 45 Recommended MPIO Registry Settings Location: HKLM\System\CurrentControlSet\Services\mpio\Parameters MSFT Default Value Recommended CML Value Setting Name Description PDORemovePeriod This setting controls the number of seconds that the multipath pseudoLUN remains in system memory. 0 60 UseCustomPathRecoveryInterval If this key exists and is set to 1. This setting is only used if it is not set to 0 and UseCustomPathRecoveryInterval is set to 1. The maximum time allowed is MAXULONG (49.000 days). When this timer value is exceeded. should never be set below 60 seconds. In most cases.Microsoft Multipath I/O Best Practices | CML1004 . and thus. This field is only honored if PathVerifyEnabled is TRUE.46 MSFT Default Value Recommended CML Value Setting Name Description PathVerificationPeriod This setting is used to indicate the number of seconds with which MPIO has been requested to perform path verification. The default setting is 3. and assuming that the I/O has been retried a fewer number of times than RetryCount). This timer is specified in seconds. The maximum allowed is MAXULONG. The default is 30 seconds. 3 no change RetryInterval This setting specifies the interval of time (in seconds) after which a failed request is retried (after the DSM has decided so.Microsoft Multipath I/O Best Practices | CML1004 . 30 no change RetryCount This setting specifies the number of times a failed I/O if the DSM determines that a failing request must be retried. The default is 1 second. This value is specified in seconds. 1 no change Dell Compellent Storage Center . This is invoked when DsmInterpretError() returns Retry = TRUE. Installing host bus adapters (HBA) or other storage controllers can cause this key to be created and configured.Microsoft Multipath I/O Best Practices | CML1004 . If MPIO is installed this value is used. 15 no change WMIRequestTimeout Timeout value set for WMI requests such as LoginToTarget. LogoutFromTarget. SendTargets. 15 35 TCPConnectTime Timeout given to TCP when a Connect request is sent.Table 5 Setting Name Description TimeoutValue Disk time-out is a registry setting that defines the time that Windows will wait for a hard disk to respond to a command. 60 90 LinkDownTime This value determines how long requests will be held in the device queue and retried if the connection to the target is lost. If MPIO is not installed MaxRequestHoldTime is used instead. 15 no change TCPDisconnectTime Timeout given to TCP when a Disconnect request is sent. Table 6 47 Recommended Disk Registry Settings Location: HKLM\SYSTEM\CurrentControlSet\Services\Disk MSFT Default Value 60 Recommended CML Value no change Recommended iSCSI Initiator Registry Settings Location: HKLM\SYSTEM\CurrentControlSet\Control\Class\{4D36E97B-E325-11CE-BFC108002BE10318}\<Instance Number>\Parameters MSFT Default Value Recommended CML Value Setting Name Description MaxRequestHoldTime Maximum number of seconds that requests are queued if connection to the target is lost and the connection is being retried. 30 no change Dell Compellent Storage Center . etc. After this hold period. requests will be failed with "error no device" and device (disk) will be removed from the system. initiator will request InitialR2T (InitialR2T=Yes). At most this many requests will be sent to the target before receiving response for any of the requests. 262144 (256KB) no change MaxBurstLength This is the negotiated Max Burst Length. the driver will attempt to re-login. 65536 (64KB) no change IPSecConfigTimeout Timeout value used when the driver calls the discovery service to configure\release IPsec for an iSCSI connection.48 MSFT Default Value Recommended CML Value Setting Name Description DelayBetweenReconnect If a connection is dropped while it is in FullFeature phase. 0 1 MaxTransferLength This is maximum data size of an I/O request. 1 no change MaxConnectionRetries Maximum number of times a lost TCP connection will be retried. -1 (indefinitely) no change MaxPendingRequests This setting controls the maximum number of outstanding requests allowed by the initiator. 15 no change InitialR2T If set to Non-Zero value. the initiator will send NOP OUT PDUs to target if there is no activity for 2 minutes.Microsoft Multipath I/O Best Practices | CML1004 . 262144 (256KB) no change FirstBurstLength This is the negotiated First Burst Length. This parameter sets the delay between each re-login attempts. Else initiator will not request InitialR2T (InitialR2T=No). 0 no change Dell Compellent Storage Center . 65536 (64KB) no change MaxRecvDataSegmentLength This is the negotiated MaxRecvDataSegmentLength. 255 no change EnableNOPOut If set to 1. Link 49 Dell Compellent Storage Center .Microsoft Multipath I/O Best Practices | CML1004 . 10 no change Note: A reboot is required for the change to take effect. Alternatively. initiator will request ImmediateData (ImmediateData=Yes). unloading and reloading the initiator driver will also cause the change to take effect. 10 no change ErrorRecoveryLevel Error recovery level that the initiator will request.Link Configuring MPIO Timers (September 2009) .MSFT Default Value Recommended CML Value Setting Name Description ImmediateData If set to Non-Zero value. look under SCSI and RAID Controllers. Right click Microsoft iSCSI Initiator and select Disable to unload the driver. 1 (Yes) no change PortalRetryCount This value is used to determine how many times a connect request to a target portal should be retried if the portal is down. Then select Enable to reload the driver. In the Device Manager GUI. Else initiator will not request ImmediateData (ImmediateData=No). 1 no change NetworkReadyRetryCount This value is used to determine how many times initiator should retry getting the IP address of NIC corresponding to the PortNumber specified in the login request. 2 no change AsyncLogoutPauseTimeout This is the number of seconds that the initiator pauses the I/O queue after receiving an async logout. Sources: Microsoft iSCSI Initiator Documentation (March 2012) . microsoft.com is focused on meeting your needs with proven services and support.aspx Multipath I/O (MPIO) Cmdlets in Windows PowerShell Reference http://technet. DellTechCenter.aspx Managing MPIO with Windows PowerShell on Windows Server 2012 http://blogs.B Additional resources Support.com/en-us/download/details.microsoft.technet.com/b/migreene/archive/2009/08/29/3277914.10).aspx Configuring iSCSI MPIO on Windows Server 2008 R2 http://blogs.10).aspxhttp://msdn.com is an IT Community where you can connect with Dell Customers and Dell employees for the purpose of sharing knowledge.com/enus/library/dd758814.com/en-us/library/ee619743(v=ws.microsoft.microsoft.aspx 50 Dell Compellent Storage Center .dell.Microsoft Multipath I/O Best Practices | CML1004 .aspx?id=30450 MPCLAIM Reference Guide http://technet. Referenced or recommended Dell Compellent publications on Knowledge Center: http://kc. best practices.microsoft.compellent.com/library/hh826113.msdn.com/en-us/library/ee619778(v=ws.aspx Microsoft MPIO Users Guide for Windows Server 2012 http://www.com/b/san/archive/2012/07/20/managing-mpio-with-windows-powershellon-windows-server-2012.com Dell Compellent Storage Center MPIO Users Guide Dell Compellent Storage Center Connectivity Guide Dell Compellent Storage Center Multipath IO (MPIO) Manager for Microsoft Servers User Guide Dell Compellent Storage Center Windows Server 2012/R2 Best Practices Guide Referenced or recommended Microsoft publications: Microsoft MPIO Step-by-Step Guide (2008 R2) http://technet. and information about Dell products and installations.