EMC Symmetrix with VERITAS Dynamic Multi-pathing (DMP)

Transcription

1 EMC Symmetrix with VERITAS Dynamic Multi-pathing (DMP) Best Practices Planning Abstract This white paper provides best practices for configuring VERITAS Dynamic Multi-pathing (DMP) in an EMC Symmetrix environment. May 2007

2 Copyright 2007 EMC Corporation. All rights reserved. EMC believes the information in this publication is accurate as of its publication date. The information is subject to change without notice. THE INFORMATION IN THIS PUBLICATION IS PROVIDED AS IS. EMC CORPORATION MAKES NO REPRESENTATIONS OR WARRANTIES OF ANY KIND WITH RESPECT TO THE INFORMATION IN THIS PUBLICATION, AND SPECIFICALLY DISCLAIMS IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Use, copying, and distribution of any EMC software described in this publication requires an applicable software license. For the most up-to-date listing of EMC product names, see EMC Corporation Trademarks on EMC.com All other trademarks used herein are the property of their respective owners. Part Number H2787 Best Practices Planning 2

3 Table of Contents Executive summary...4 Introduction...4 Audience... 4 Confirming DMP qualification...4 Configuration guides... 5 Symmetrix port flags...5 Common_Serial_Number (CMSN or C-bit)... 5 Disable_Q_Reset_on_UA (DQRS or D-bit)... 6 DMP and PowerPath...6 HBA and host settings...6 Conclusion...7 References...7 Best Practices Planning 3

4 Executive summary VERITAS Dynamic Multi-pathing (DMP) is a component of VERITAS Storage Foundation that provides path failover and load balancing for a variety of open systems operating systems. EMC provides settings and requirements to ensure that DMP operates properly in a Symmetrix environment. If these requirements are not met, DMP may not load balance or fail over correctly, leading to a possible outage if a component in the I/O path fails. Introduction This white paper will examine what resources must be used to ensure that VERITAS DMP is properly configured for use in a Symmetrix environment. This includes proper configuration of Symmetrix director flags, host settings, and HBA settings. It will also discuss how to confirm general support, integration with other multi-pathing products, and operating system patch and driver levels. Audience This white paper is intended for storage architects, storage administrators, or systems administrators who will be planning for or installing VERITAS Dynamic Multi-pathing in a Symmetrix environment. Confirming DMP qualification There are several methods of determining what versions of VERITAS VxVM and, by extension, what versions of VERITAS DMP are qualified for use with EMC Symmetrix storage arrays. The recommended method is through the use of the EMC E-Lab Interoperability Navigator. E-Lab Interoperability Navigator is an online query tool that allows users to access comprehensive interoperability information from EMC E-Lab. It can be accessed at the following URL: E-Lab Navigator allows the user to load their configuration into the utility and generate support statements that are customized to the user s environment and contain qualified configurations, patches, and required settings. The following paths within E-Lab Navigator can be used to enter the correct information regarding VERITAS and DMP into a search cart. For multipathing software: Software > Infrastructure Software > Veritas For VERITAS Volume Manager: Server > Server LVM > Veritas > VxVM Besides containing qualification information, footnotes in the support statements generated by E-Lab Navigator contain notes that are relevant to DMP qualification, patches, host and Symmetrix settings, and other relevant information. Figure 1 is an example of a VERITAS Volume Manager support statement that was generated using E-Lab Navigator. Best Practices Planning 4

5 Figure 1. VERITAS Volume Manager support statement in E-Lab Navigator The statement contains a DMP column that indicates whether DMP is supported with the chosen array, as well as footnotes indicating any restrictions and required patches or settings with that particular combination of Volume Manager version, operating system version, and storage array model. Another method of checking for qualification is through the use of the EMC Support Matrix, which can be downloaded from the following URL: Configuration guides Along with E-Lab Navigator and the EMC Support Matrix, information about configuring DMP can be found in the connectivity guides for the various host platforms that are supported with VERITAS and Symmetrix. These guides can be downloaded from Powerlink ( EMC s password-protected customer- and partner-only extranet. The following page within Powerlink (Customer view) contains a list of the available host connectivity guides: Home > Support > Documentation/White Paper Library > Host Connectivity/HBAs > Installation/Configuration The guides may contain notes regarding DMP as well as non-dmp related information and system settings and should be consulted whenever connecting a host to a Symmetrix storage array. Symmetrix port flags There are Symmetrix port flags (also commonly called director flags or director bits) that must be set in certain configurations so that DMP will configure devices properly and operate correctly. These settings will be noted in E-Lab Navigator, the support matrix, and in the host connectivity guides. The following are the flags that must often be set in a DMP environment: Common_Serial_Number (CMSN or C-bit) This flag should be enabled for multipathed configurations or hosts that need a unique serial number to determine which paths lead to the same device. The following output from syminq shows two special device file entries for sym device 711 from a Solaris host. The output shows that the Common_Serial_Number flag is set because the device serial numbers returned by a SCSI inquiry both end in 000. Best Practices Planning 5

6 Device Product Device Name Type Vendor ID Rev Ser Num Cap (KB) /dev/rdsk/c2t17d34s2 EMC SYMMETRIX /dev/rdsk/c3t16d34s2 EMC SYMMETRIX Without the C-bit set, the last three digits of the device serial number would indicate which FA and port the device was being accessed on. In the following example, device 711 is being accessed on FA-1aA (010) and FA-16aB (161). Device Product Device Name Type Vendor ID Rev Ser Num Cap (KB) /dev/rdsk/c2t17d34s2 EMC SYMMETRIX /dev/rdsk/c3t16d34s2 EMC SYMMETRIX A multipathing product such as DMP that requires unique serial numbers to determine if a device is multipathed would see these paths to device 711 as two different devices and would not be able to configure load balancing or failover for this device. Disable_Q_Reset_on_UA (DQRS or D-bit) When the Disable Queue Reset on Unit Attention flag is enabled, a Unit Attention (UA) that is propagated from another director does not flush the queue for this device on this director. It is used for hosts that do not expect the queue to be flushed on a 0629 sense (only on a Hard Reset). There are some DMP configurations where the D-bit is required, some where it is not required, and some where it is optional. Please ensure that this flag is correctly set for any environment where DMP is in use. DMP and PowerPath In most situations, PowerPath and DMP can coexist on a host provided that all requirements are met. Please reference the PowerPath Product Guide, Installation and Administration Guide, and Release Notes for the version of PowerPath that will be installed to ensure that it is configured properly. The documentation can be found on Powerlink at the following location (Customer view): Home > Support > Documentation/White Paper Library > Software P-R > PowerPath Some configuration requirements exist for DMP and not for PowerPath. For example, PowerPath does not require either the C- or D-bit to be set on the directors. However, the C-bit must be set when DMP is installed and the D-bit is often required. To ensure that DMP functions properly, these flags need to be set correctly whether PowerPath is installed or not installed. Unless otherwise noted, settings that are required for DMP are either the same for PowerPath or should be enabled with or without PowerPath present. HBA and host settings Incorrectly configured HBA or host parameters, such as the SCSI disk driver I/O time-out value, can cause DMP not to fail over or load balance properly. EMC and HBA vendor documentation will help you determine the correct settings. HBA installation and configuration guides that are available from EMC can be found in the following location on Powerlink (Customer view): Home > Support > Documentation/White Paper Library > Host Connectivity/HBAs > Installation/Configuration Best Practices Planning 6

7 Installation and configuration guides covering all other HBA models and platforms can be found on the support or download pages at the website of the HBA manufacturer or operating system vendor. Where the manuals can be found will depend on whether the driver and firmware being used were written by the HBA manufacturer or by the OS vendor. HBA settings for DMP are generally the same as those used with EMC PowerPath. Conclusion VERITAS Dynamic Multi-pathing (DMP) is a component of VERITAS Storage Foundation that provides path failover and load balancing for a variety of open systems operating systems. To ensure that DMP is configured properly, EMC provides settings and requirements so DMP will function correctly in a Symmetrix environment. Not meeting these requirements may lead to a possible outage if a component in the I/O path fails. This white paper detailed where configuration information on Symmetrix director flags, host settings, and HBA settings can be found. It also discussed how to confirm general support, integration with other multipathing products, and operating system patch and driver levels. References Before attaching a host with DMP to Symmetrix, VERITAS documentation should be consulted to ensure that DMP has been configured correctly for both load balancing and failover. Symantec support can be reached at The following documents are available on Symantec s website and contain information about supported configurations as well as the installation and administration of DMP. VERITAS Volume Manager Administrator s Guide VERITAS Storage Foundation Release Notes VERITAS Storage Foundation Installation Guide Hardware Compatibility List for VERITAS Storage Foundation and High Availability Solutions VERITAS Storage Foundation and High Availability Solutions by Symantec Hardware TechNote Best Practices Planning 7