Storage Multi-Pathing choices in HP-UX Serviceguard environments, August 2009

ManualsBrandsHP ManualsSoftwareHP Serviceguard Storage Management Suite Software

Storage Multi-Pathing choices in HP-UX Serviceguard

environments

Version 1.1

Abstract.............................................................................................................................................. 2

Executive summary............................................................................................................................... 2

Definition of terms................................................................................................................................ 3

Multi-pathing product reference documentation ....................................................................................... 3

Typical Cluster Storage Configuration .................................................................................................... 5

Active/Passive Storage Systems......................................................................................................... 7

Active/Active Storage Systems .......................................................................................................... 7

Multi-Pathing solutions on HP-UX 11i v2 ................................................................................................. 8

Volume Manager based ................................................................................................................... 9

LVM PVlinks................................................................................................................................. 9

VxVM/CVM Dynamic Multi-pathing (DMP)...................................................................................... 9

Storage platform specific multi-pathing solutions ................................................................................ 10

HP StorageWorks SecurePath ...................................................................................................... 11

EMC PowerPath ......................................................................................................................... 12

Multi-pathing solutions for HP Virtual Machine................................................................................... 12

Selection and coexistence of different multi-pathing solutions............................................................... 12

Multi-Pathing solutions on HP-UX 11i v3 ............................................................................................... 13

Native Multi-Pathing and LVM PVlinks (Alternate Links).................................................................... 14

Native Multi-Pathing and VxVM/CVM Dynamic Multi-pathing (DMP)................................................ 14

HP StorageWorks SecurePath ...................................................................................................... 14

EMC PowerPath ......................................................................................................................... 15

Summary and Recommendation .......................................................................................................... 15

For more information.......................................................................................................................... 16

Summary of content (16 pages)

PAGE 1
Storage Multi-Pathing choices in HP-UX Serviceguard environments Version 1.1 Abstract.............................................................................................................................................. 2 Executive summary............................................................................................................................... 2 Definition of terms...................................................................................................................
PAGE 2
Abstract Serviceguard protects users and applications from a variety of failures (e. g. software, system, and network failure to name a few) by forming a cluster of multiple nodes and providing sufficient redundancy to remove single points of failure from the configuration. In general, Serviceguard directly provides the failure protection while in specific areas it relies on other technology to add redundancy.
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Definition of terms Table 2. Term Definition CFS Serviceguard Cluster File System based on Veritas CFS from Symantec; included in some of the HP Serviceguard Storage Management Suite bundles. CVM Veritas Cluster Volume Manager from Symantec; included in some of the HP Serviceguard Storage Management Suite bundles. DMP Dynamic Multi Pathing; Symantec’s multi-pathing product for VxVM and CVM volume manager DSF Device Special File; a special file used to interface with devices – e. g.
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– Migrating from HP StorageWorks SecurePath for Active-Active Disk Arrays to Native Multipathing in HP-UX 11i v3 (http://docs.hp.com/en/AA-RWF2A-TE/AA-RWF2A-TE.pdf)  Third party mass storage devices (http://www.hp.com/products1/serverconnectivity/mass_storage_devices.html)  Identifies the storage devices validated for use with HP-UX. Specifies which of these is not supported with LVM PVlinks, and which require third party multi-pathing software, such as EMC PowerPath for Serviceguard support.
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Chapter 8 ”VxVM 4.1, New Style DSFs and HP-UX Native Multipathing” explains how VxVM and DMP 4.1 interoperate with the new mass storage subsystem.  EMC PowerPath for HP-UX Version 4.5 Installation and Administration Guide (P/N 300-002-838, Rev A03) Describes how to install/uninstall PowerPath with VxVM with specific array types. Describes when to use PVlinks with PowerPath, and migrating from SecurePath to PowerPath. To obtain a copy of this document, registration is required at: http://powerlink.emc.
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Figure 1: Typical Cluster Storage Configuration Node-B Node-A Atention Fault Run Remote SPPr esent StandbyPower Power Atention Fault Run Remote SPPr esent StandbyPower Power h p Integrity rx7640 h p Integrity rx7640 HBA-3 HBA-2 HBA-1 HBA-4 2 1 4 3 h p S to ra g e W o rk s E d g e S w itc h 2 /1 6 h p S to ra g e Wo rk s E d g e S w itc h 2 /1 6 1 0 /1 0 0 1 0 /1 0 0 P WR E RR IM L 1 5 1 4 1 3 1 2 1 1 10 9 8 7 6 5 4 3 2 1 P WR ERR IM L 0 15 1 4 1 3 1 2 1 1 10 F
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Active/Passive Storage Systems With Active/Passive storage systems, one controller is assigned to a LUN as primary controller (owner of the LUN) and handles all the I/O requests to it. The other controller – or multiple other controllers, if available – acts as standby controller. The standby controller of a LUN only issues I/O requests to it, if their primary controller failed. To achieve load balancing it makes sense to distribute the LUNs evenly among the controllers.
PAGE 8
I/O requests travel through multiple layers of software and hardware from the application which issued the initial request to the storage system and back. Load balancing multi-pathing software and volume managers are two of the layers which need to be configured carefully to allow those readahead mechanisms to work successfully with sequential read operations.
PAGE 9
Symantec DMP yes yes no yes4 yes HP Storage Works SecurePath® yes yes yes no no EMC PowerPath® yes yes yes no no Volume Manager based Serviceguard supports two different volume managers which also provide a multi-pathing solution. If customers choose LVM or SLVM as their volume manager, protection against path failures is provided by failover to alternate links using LVM PVlinks (a.k.a. Alternate Links).
PAGE 10
Multipathing white paper goes into further details about the different load balancing policies and interoperability with other multi-pathing solutions. VxVM’s configuration daemon creates its own path-independent device files in /dev/vx/rdmp and /dev/vx/dmp at boot up time. It uses one device file per LUN or disk – not per path. Multiple paths (SUBPATH) are associated with VxVM/DMP devices files. Figure 3 shows how to identify which paths are associated with a specific device.
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since they are tightly integrated with the array vendor’s storage systems, their support is often limited to only that vendors storage arrays. HP StorageWorks SecurePath HP StorageWorks SecurePath for HP-UX is a purchasable software product and the current version (3.0FSP2 Patch2) provides highly available access to active/active and active/passive HP disk arrays for HP-UX 11i v2 or earlier. SecurePath provides automatic failover across the paths of the individual storage device (LUN).
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/dev/dsk/c6t0d1 Active /dev/dsk/c8t0d1 Active ================================================================== In addition to path failover and load balancing, SecurePath also monitors the path’s health to allow automatic fail-back after a path is repaired and to proactively identify issues with idle paths. For more information about HP StorageWorks SecurePath please see the “HP StorageWorks SecurePath 3.0F Service Pack 2 for HP-UX 11i v1.0 and 11i v2.0, installation and reference guide”.
PAGE 13
availability to have more than one multi-pathing solution providing services for the same device or LUN nor is it supported. It might even be counterproductive having multiple multi-pathing solutions installed. DMP, SecurePath, and PowerPath all try to provide multi-pathing to all devices they find during a discovery process, therefore the administrator has to ensure that only one product is active for specific LUN or sometimes a specific pair of controllers.
PAGE 14
Storage Vendor provided ‘plug-ins’ are needed to provide multi-pathing support of active/passive arrays with Native Multi-Pathing on HP-UX 11i v3. Asymmetrical active/active arrays (active/active arrays with a preferred controller) that are capable of Asymmetric Logical Unit Access (ALUA) do not need a plug-in to work with Native Multi-Pathing as ALUA support has been implemented and delivered in the HP-UX mass storage stack with 11i v3 Update 1 (fusion 0709).
PAGE 15
automatically configured, fully integrated with the rest of HP-UX and can be used with all the HP-UX I/O commands. HP-UX 11i v3 does not support HP StorageWorks active/passive disk arrays. If you are using an active/passive EVA 3000 or 5000 disk arrays, you must upgrade the firmware to an active/active version.
PAGE 16
For more information To learn more about the new mass storage on HP-UX 11i v3 see the following documents on the HP documentation websites (http://docs.hp.com and http://docs.hp.com/en/oshpux11iv3.