Preventive Service Planning
Abstract
The recommended multi-path driver to use on IBM AIX and VIOS when attached to SVC and Storwize storage devices running microcode levels V7.6.1 and later is changing from the SDD PCM to the default AIX PCM.
Content
We recommend that new AIX deployments use the default AIXPCM.
For existing deployments clients can chose to migrate to the AIXPCM or remain on SDDPCM.
This includes VIO servers providing storage resources to IBMi lpars.
SDDPCM is not supported on Power9 servers.
Prerequisite OS Levels
AIX 7.1 TL3
AIX 7.2 any TL
VIOS 2.2.4.0
Why is this change being made?
The AIXPCM has evolved to include all significant functionality provided by SDDPCM.
The AIXPCM has the advantage over SDDPCM of not requiring specific maintenance. All updates are applied as part of the Operating System Maintenance.
Reference
Refer to the SDDPCM users guide for instructions on removing the SDDPCM from your system.
http://www-01.ibm.com/support/docview.wss?uid=ssg1S7000303
Note1: Removing SDDPCM will set the queue to the default value of 20. Any modification made to the queue depth prior to removal will need to be reapplied.
Note2: The default path selection algorithm for AIXPCM is "fail_over". The AIX PCM supports the "shortest_queue" algorithm which is similar to SDD PCM's "load_balance" algorithm. The chdev command may be used to set the algorithm, though it may also be necessary to set the reserve policy when changing the algorithm. For example, to set hdisk5 to use the "shortest_queue" algorithm, execute this command:
chdev -l hdisk5 -a algorithm=shortest_queue -a reserve_policy=no_reserve
Note3: Multipath management commands differ between AIXPCM and SDDPCM. If the SDDPCM is removed from your system any scripts that have been generated that utilize these commands will need to be modified to use the corresponding AIXPCM commands.
Refer to the following links for the complete list of path management commands for MPIO using the AIXPCM.
MPIO-capable device management
https://www.ibm.com/support/knowledgecenter/ssw_aix_72/com.ibm.aix.osdevice/devmpio.htm
Reference to lsmpio command
https://www.ibm.com/support/knowledgecenter/ssw_aix_72/com.ibm.aix.cmds3/lsmpio.htm
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Document Information
Modified date:
10 June 2021
UID
ssg1S1010218