B    Clearing Persistent Reservations on Disks Behind HSZ80 and HSG80 Controllers

TruCluster Server cluster members use persistent reservations to coordinate access to shared storage. These persistent reservations control access to devices and logical volumes, and are used to erect a barrier against any system that is not a member of the current cluster.

The base operating system does not know how to manage these persistent reservations. Attempts by the base operating system to access a disk that has a persistent reservation will return I/O error messages. All I/O attempts will fail.

If you boot (or reinstall) the base operating system on a system that attempts to access disks that were previously used by a cluster behind an HSZ80 or HSG80 controller, the base operating system might not be able to see the disks. This is most likely because the disk participated previously in a cluster, and one of the cluster members set a reservation on the disk to prohibit any other hosts (or noncluster members) on this shared bus from accessing the disk. The problem is that the reservation was not cleared when the cluster member or the cluster was shut down.

To remove the reservations, use the /usr/sbin/cleanPR clean command. The cleanPR script finds and clears all persistent reservations from the attached HSZ80 and HSG80 devices.

Caution

Do not run the cleanPR script on a system that is in a cluster. You do not want to remove reservations that the running cluster is using to actively control disk access. Doing so can result in data corruption.

There are two scenarios to consider. In the first scenario, you can boot a disk containing the base operating system and run the cleanPR command. In the second scenario, you are trying to install the base operating system on a disk that is behind an HSG80 or HSZ80 controller, has a persistent reservation on it, and does not have an installed version of the base operating system.

For the first scenario, if you encounter persistent reservations when attempting to access storage that was previously used in a cluster, boot the operating system and enter the /usr/sbin/cleanPRclean command to clear the reservations.

The second scenario is more complex because you do not have a running version of the operating system from which you can run the cleanP script. However, the cleanPR script is on the Tru64 UNIX Operating System CD-ROM. Therefore, you can start the installation from CD-ROM, get to the single-user shell, and enter the /usr/sbin/cleanPR clean command to clear the reservations.