Verifying Data Storage Arrays Using the vxfentsthdw Utility

You can use the vxfentsthdw utility to verify that shared storage arrays to be used for data support SCSI-3 persistent reservations and I/O fencing. The description in Chapter 3 shows how to use the testing utility to test a single disk. The utility has other options that may be more suitable for testing storage devices in other configurations.

The utility, which you can run from one system in the cluster, tests the storage used for data by setting and verifying SCSI-3 registrations on the disk or disks you specify, setting and verifying persistent reservations on the disks, writing data to the disks and reading it, and removing the registrations from the disks. Refer also to the vxfentsthdw(1M) manual page.

General Guidelines for Using vxfentsthdw

• The utility requires two systems connected to the shared storage.

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 Caution    The tests overwrite and destroy data on the disks, unless you use the -r option.

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• The two systems must have remsh permission set so that each node has root user access to the other. Temporarily modify the /.rhosts file to enable cluster communications for the vxfentsthdw utility, placing a "+ +" character in the first line of the file. You can also limit the remote access to specific systems. Refer to the manual page for the /.rhosts file for more information. See Removing remsh Permissions and Restoring Public Network Connections when you complete testing.
• To ensure both systems are connected to the same disk during the testing, you can use the vxfenadm -i diskpath command to verify a disk's serial number. See Verifying the Nodes See the Same Disk.
• For disk arrays with many disks, use the -m option to sample a few disks before creating a disk group and using the -g option to test them all.
• When testing many disks with the -f or -g option, you can review results by redirecting the command output to a file.
• The utility indicates a disk can be used for I/O fencing with a message resembling:

  The disk /dev/rdsk/c4t8d0s2 is ready to be configured for I/O 
  Fencing on node nebula

If the utility does not show a message stating a disk is ready, verification has failed.

• If the disk you intend to test has existing SCSI-3 registration keys, the test issues a warning before proceeding.

vxfentsthdw Options

The table below describes three methods the utility provides to test storage devices.

Using the -r Option for Non-destructive Testing

To test disk devices containing data you want to preserve, you can use the -r option with the -m, -f, or -g options, which are described in the following sections. For example, to use the -m option and the -r option, you can run the utility by entering:

When invoked with the -r option, the utility does not use tests that write to the disks. Therefore, it does not test the disks for all of the usual conditions of use.

Using the -m Option

The -m option for vxfentsthdw is described in detail in chapter 3.

Using the -f Option

Use the -f option to test disks that are listed in a text file. For example, you can create a file to test two disks shared by systems galaxy and nebula that might resemble:

where the first disk is listed in the first line and is seen by galaxy as /dev/rdsk/c2t2d1s2 and by nebula as /dev/rdsk/c3t2d1s2. The other disk, in the second line, is seen as /dev/rdsk/c2t2d2s2 from galaxy and /dev/rdsk/c3t2d2s2 from nebula. Typically, the list of disks could be extensive.

Suppose you created the file named disks_blue. To test the disks, you would enter:

The utility reports the test results one disk at a time, just as for the -m option.

You can redirect the test results to a text file. Precede the command with "yes" to acknowledge that the testing destroys any data on the disks to be tested.

For example:

Using the -g Option

Use the -g option to test all disks within a disk group. For example, you create a temporary disk group consisting of all disks in a disk array and test the group.

The utility reports the test results one disk at a time. You can redirect the test results to a text file for review.

After testing, destroy the disk group and put the disks into disk groups as you need.

Testing a Disk with Existing Keys

If the utility detects that a coordinator disk has existing keys, you see a message that resembles:

The utility prompts you with a warning before proceeding. You may continue as long as I/O fencing is not yet configured.