The shared storage for VCS must support SCSI-3 persistent reservations to enable I/O fencing. VCS involves two types of shared storage:
Act as a global lock during membership changes. Coordinator disks are small LUNs (typically three per cluster) |
Perform the following checks for I/O fencing disks:
List the disks on each node and pick three disks as coordinator disks.
For example, execute the following commands to list the disks:
Use the vxfentsthdw utility to test the shared storage arrays support SCSI-3 persistent reservations and I/O fencing. Review the guidelines to run vxfentsthdw program, verify that the systems see the same disk, and proceed to test the disks. Make sure to test disks serving as coordinator disks.
See Setting up coordinator disk groups
The vxfentsthdw utility has additional options suitable for testing many disks. Review the options for testing disk groups (-g
) and disks listed in a file (-f
).
You can also test disks without destroying data using the -r
option.
Review these guidelines for using vxfentsthdw
Caution
The tests overwrite and destroy data on the disks unless you use the -r
option.
ssh
(default) or rsh
communication. If you use rsh
, launch the vxfentsthdw utility with the -n
option.
See Enabling communication between systems
After completing the testing process, remove permissions for communication and restore public network connections.
vxfenadm -i
diskpath
command to verify the disk serial number.
Verifying the nodes see the same disk
To confirm whether a disk (or LUN) supports SCSI-3 persistent reservations, two nodes must simultaneously have access to the same disks. Because a shared disk is likely to have a different name on each node, check the serial number to verify the identity of the disk. Use the vxfenadm
command with the -i
option to verify that the same serial number for the LUN is returned on all paths to the LUN.
For example, an EMC disk is accessible by the /dev/sdr path on node A and the
/dev/sdt path on node B.
SCSI ID=>Host: 2 Channel: 0 Id: 0 Lun: E
The same serial number information should appear when you enter the equivalent command on node B using the /dev/sdt path.
On a disk from another manufacturer, Hitachi Data Systems, the output is different and may resemble:
SCSI ID=>Host: 2 Channel: 0 Id: 0 Lun: E
Refer to the vxfenadm(1M)
manual page.
Testing the disks using vxfentsthdw script
This procedure uses the /dev/sdr disk in the steps.
If the utility does not show a message stating a disk is ready, verification has failed. Failure of verification can be the result of an improperly configured disk array. It can also be caused by a bad disk.
If the failure is due to a bad disk, remove and replace it. The vxfentsthdw utility indicates a disk can be used for I/O fencing with a message resembling:
The disk /dev/sdr is ready to be configured for I/O Fencing on node north
See Adding or removing coordinator disks
To test disks using vxfentsthdw script
******** WARNING!!!!!!!! ********
THIS UTILITY WILL DESTROY THE DATA ON THE DISK!!
Do you still want to continue : [y/n] (default: n) y
Enter the disk name to be checked for SCSI-3 PGR on node
north in the format: /dev/sdx
Enter the disk name to be checked for SCSI-3 PGR on node
south in the format: /dev/sdx
Make sure it's the same disk as seen by nodes north and south
If the disk names are not identical, then the test terminates.
The disk is now ready to be configured for I/O Fencing on node north
ALL tests on the disk /dev/sdr have PASSED
The disk is now ready to be configured for I/O Fencing on node north