IBM Support

Migrate to AIXPCM using "Manage_Disk_Drivers" Command

How To


Summary

Using the "manage_disk_drivers" command allows users to switch Path Control Modules on an AIX system without direct or extended application impact.
However, a reboot of the host is required to make the change effective.
When migrating to AIXPCM in a PowerHA configuration, this procedure can be performed on one side of the cluster first, reboot, then proceed with the other side of the cluster

Objective

The objective is to allow customers to migrate away from SDDPCM multi-pathing and onto AIXPCM in response to the End of support (EOS) for SDDPCM with IBM storage products. The support for SDDPCM officially ceased on June 30, 2020.

Environment

AIX stand-alone LPARs, VIO Clients, VIOS , supporting VSCSI or NPIV adapter configurations.
This procedure can be used in host cluster environments, such as PowerHA, Oracle, DB2 and Spectrum Scale(GPFS), single node at a time.
When migrating to AIXPCM in a PowerHA or other cluster configuration, this procedure can be performed on one side of the cluster first, reboot, then proceed with the other side of the cluster.
Power 9 hardware platforms and related OS levels were not tested with SDDPCM, only AIXPCM. Therefore, P9 does not support SDDPCM on any version of AIX.

Steps

The "manage_disk_drivers" command allows administrators to choose between different Path Control Modules (PCMs), or between using a PCM and configuring the disks as non-MPIO disks. It is the easiest and less intrusive method for transitioning from SDDPCM to AIX MPIO default PCM.
Example of using the manage_disk_drivers command to switch from SDDPCM to AIX PCM for a system that is using IBM SVC 2145 or DS8K disks.
Note: Performing migration on VIO server requires executing the procedure from root prompt.
STEP 1: Setup disk predefined attributes to have correct defaults for SVC 2145 or DS8K storage.
These values should be applied BEFORE rebooting your system into AIXPCM mode.
The values of the attributes of the disks are not preserved during this conversion.  
In particular, the AIX default PCM uses the "single_path" reservation policy as the default, and the "fail_over" algorithm as the default algorithm.
If the disks being switched from SDDPCM to AIX PCM are shared among multiple nodes in a cluster or VIOS configuration, this default reservation policy must be changed before the disk is opened.  
If this is not changed, other nodes in the cluster or VIOS configuration will lose access to the shared disks until the reservation policy is changed.

a) For SVC storage:
# chdef -a reserve_policy=no_reserve -c disk -s fcp -t mpioosdisk
reserve_policy changed

# chdef -a queue_depth=32 -c disk -s fcp -t mpioosdisk
queue_depth changed

# chdef -a rw_timeout=30 -c disk -s fcp -t mpioosdisk
rw_timeout changed

# chdef -a algorithm=shortest_queue -c PCM -s friend -t fcpother
algorithm changed
b) For DS8K storage, complete the same steps specifying type "aixmpiods8k":
# chdef -a reserve_policy=no_reserve -c disk -s fcp -t aixmpiods8k
reserve_policy changed


# chdef -a queue_depth=32 -c disk -s fcp -t aixmpiods8k
queue_depth changed

# chdef -a rw_timeout=30 -c disk -s fcp -t aixmpiods8k
rw_timeout changed

# chdef -a algorithm=shortest_queue -c PCM -s friend -t fcpother
algorithm changed

Please take note of the following important information:
Note 1: Any future LUN will now have the recommended values.
Existing disks will acquire new attribute settings once reboot is completed.
Note 2: 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.
Note 3: 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
Note 4: Multi-path 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.
STEP 2: Save the information about base-customized devices in the Device Configuration database onto the boot device.
# savebase -v
# sync; sync; sync
STEP 3: Important! Run "bosboot".
A "bosboot" must be executed when the "chdef" command has been issued prior to a reboot to avoid losing changes to the ODM.
# bosboot -ad /dev/ipldevice
STEP 4 (optional):  List available PCM options.
Based on the type of storage controller configured, you can run the command to list out the available options.
The "-l" option shows a list of all options available (the columns show the device family, the driver currently used by that family, and the different options available).
# manage_disk_drivers -l | grep -i svc 

IBMSVC         NO_OVERRIDE     NO_OVERRIDE,AIX_AAPCM,AIX_non_MPIO
or
# manage_disk_drivers -l | grep -i 2107ds8k

2107DS8K       NO_OVERRIDE     NO_OVERRIDE,AIX_AAPCM,AIX_non_MPIO
The "NO_OVERRIDE" option indicates that the configuration is not overridden by manage_disk_drivers, and so the device family is configured based on the available ODM to match that family.
The ODM supplied by SDDPCM takes precedence over the AIX default PCM ODM.  
So a value of "NO_OVERRIDE" indicates that SDDPCM is used to configure devices of that family, if SDDPCM is installed.  
If SDDPCM is not installed, then the AIX default PCM is used.
STEP 5:  Run the "manage_disk_drivers" command to switch to AIX PCM.
# manage_disk_drivers -d IBMSVC -o AIX_AAPCM
or
# manage_disk_drivers -d 2107DS8K -o AIX_AAPCM
By selecting the "AIX_AAPCM" option, the administrator can instruct AIX to use the AIX default PCM even if SDDPCM is installed.
STEP 6: Edit the "/etc/inittab".

a) To list "pcmsrv" record in the "/etc/inittab" file, type:
# lsitab pcmsrv
b) Comment out the line which references "pcmsrv" or remove it using "rmitab" command.
To remove pcmsrv record from the /etc/inittab file, type the following at the command prompt:
# rmitab pcmsrv
STEP 7: Reboot.
The AIX LPAR must be rebooted in order for the disks to be reconfigured to use the AIX PCM. 
# shutdown -Fr
STEP 8: Confirm AIX PCM is in control i.e. output from "lsmpio".
# lsmpio

  name    path_id  status   path_status  parent  connection


  hdisk2  0        Enabled  Non          fscsi0  50050768011006c4,0

  hdisk2  1        Enabled  Opt          fscsi0  500507680110062b,0

  hdisk2  2        Enabled  Non          fscsi1  50050768011006c4,0

  hdisk2  3        Enabled  Sel,Opt      fscsi1  500507680110062b,0

  hdisk3  0        Enabled  Opt          fscsi0  50050768011006c4,1000000000000

  hdisk3  1        Enabled  Non          fscsi0  500507680110062b,1000000000000

  hdisk3  2        Enabled  Sel,Opt      fscsi1  50050768011006c4,1000000000000

  hdisk3  3        Enabled  Non          fscsi1  500507680110062b,1000000000000
STEP 9: Uninstall SDDPCM filesets.
Once AIX is rebooted, SDDPCM is no longer in use for the disk family specified in the "manage_disk_drivers" command.  
If no disks are using SDDPCM, then the SDDPCM filesets may be uninstalled running the "installp -ug" command.
# installp -ug devices.sddpcm.72.rte devices.fcp.disk.ibm.mpio.rte

Additional Information

Contact the IBM Support Center to obtain assistance, or if there are questions and concerns.

Document Location

Worldwide

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Document Information

Modified date:
06 November 2023

UID

ibm11111227

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