Standard and persistent reservations

The SCSI Reserve command and the SCSI Persistent Reserve command are specified by the SCSI standards. Servers can use these commands to prevent ports in other servers from accessing particular LUNs.

Reserving LUNs prevents accidental data corruption that is caused when a server overwrites data on another server. The Reserve and Persistent Reserve commands are often used by clustered-system software to control access to system volumes.

If a server is not shut down or removed from the server system in a controlled way, the standard and persistent reservations of the server are maintained. Reservations prevent other servers from accessing data that is no longer in use by the server that holds the reservation. In this situation, you might want to release the reservation to allow a new server to access the volume.

When possible, have the server that holds the reservation explicitly release the reservation to ensure that the server cache is flushed and that the server software is aware that access to the volume was lost. In circumstances where this action is not possible, you can use operating-system-specific tools to remove reservations. Consult the operating system documentation for details.

When you use the rmvdiskhostmap CLI command or the management GUI to remove host mappings, system nodes remove the standard reservations and persistent reservations that the host has on the volume.