Checking SCSI3 compatibility for fencing coordinator disks
Based on the common escalations that I had handled for the fencing module in Veritas Cluster Server Product in the SAMG Division, one frequently visited aspect is to check the SCSI3 comaptibility the coordinator disks used for fencing.
As a best practice, it is always better to run the vxfentsthdw utility to check if the intended coordinator disks are infact, SCSI3 compatible. This step is a pre-requisite before installing/configuring fencing module in 'enabled' state for SCSI3 mode or 'customized' mode provided atleast one SCSI3 disk is involved.
However in some cases especially scenarios for array qualification, we have noticed that vxfentsthdw returns success because the underlying VxVM-DMP module returns success even if the intended operation did not succeed. Hence to make sure such scenarios are not applicable in your environment, it is better to run the following commands, in addition to running vxfentsthdw utility on the coordinator disks:
1. Register key:
- vxfenadm -m -k <key> -f <diskpath> -- Reserves a key on the disk mentioned through the path
- vxfenadm -g all -f <diskpath> -- Should list the above key registered on the diskpath.
If the list of keys displayed through above command does not indicate <key> then the disks may not be completely SCSI3 compatible.
2. Remove key:
- vxfenadm -x -k <key> -f /etc/vxfentab -- Removes a registered key on the disk mentioned through the path.
- vxfenadm -g all -f <diskpath> -- Should list without the above key registered on the diskpath as key is removed with the previous step.
If the list of keys displayed through above command indicates <key> still registered inspite of using 'vxfenadm -x' to remove it, then the disks may not be completely SCSI3 compatible.