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Abstract
Hosts using SCSI-2 reservations may experience loss of access, during upgrade of Spectrum Virtualize systems which have NPIV enabled.
This is due to a Spectrum Virtualize software issue, APAR HU01894, which affects software versions 7.7.0.0 - 8.2.1.10, as well as 8.3.0.x.
The issue is fixed in 8.2.1.11 and 8.3.1.0 or above. Systems without NPIV enabled are not affected.
Content
AIX or VIOS hosts may default to using SCSI-2 reservation to control access to vdisks presented by a Spectrum Virtualize system.
If NPIV is enabled, it is possible for a SCSI-2 reservation to become stuck if a node goes offline - for example, because a software upgrade is in progress. This can cause loss of access for the host system, until the host issues a lun reset to clear the reservation.
Recommended configuration change to prevent loss of access during upgrades
Ensure that no AIX server hdisks have a reserve_policy of single_path before upgrading from an affected code level.
If you are using Virtual SCSI, check the reserve_policy of the VIOS server's hdisks.
1. Check whether any hdisks have a reserve_policy of single_path.
The following shell script commands will list all affected hdisks:
lsdev -c disk <PIPE> while read disk x
do
lsattr -El $disk <PIPE> grep '^reserve_policy' <PIPE> while read x policy x x settable
do
if [ "$policy" = "single_path" ]; then
echo "$disk: $policy: $settable"
fi
done
done
2. Change the reserve_policy to no_reserve for any hdisks found in step 1.
If the shell script above shows "True+" in the right hand column, then reserve_policy can be changed online using these commands:
- chdev -l hdisk<n> -a reserve_policy=no_reserve -a algorithm=round_robin -U
- Or on a VIOS server as padmin: chdev -dev hdisk<n> -attr reserve_policy=no_reserve algorithm=round_robin
If the shell script shows "True" in the right hand column, then reserve policy can be changed, but will only be effective after a reboot:
- chdev -l hdisk<n> -a reserve_policy=no_reserve -a algorithm=round_robin -P
- Or on a VIOS server as padmin: chdev -dev hdisk<n> -attr reserve_policy=no_reserve algorithm=round_robin -perm
3. Change the default reserve_policy
If any hdisks were found to have a reserve_policy other than no_reserve, you should also change the default reserve_policy for your FC MPIO disks by running this command:
chdef -a reserve_policy=no_reserve -c disk -s fcp -t mpioosdisk
This command will set the default for the FC MPIO hdisks to be no_reserve so that all FC MPIO hdisks will be configured with no_reserve as their reserve_policy.
The bosboot command will need to be run followed by rebooting the system, to make the change effective.
Fix
APAR HU01894 is fixed in Spectrum Virtualize 8.2.1.11, and 8.3.1.0 or above. However, this fix only takes effect once the upgrade to the fixed software has completed.
Implement the recommended configuration change above, to prevent the problem occurring during upgrade to the fixed software.
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Document Information
Modified date:
28 March 2023
UID
ibm16326841