Administering Disk Sets

Disk sets can be created and configured by using the Solaris Volume Manager command-line interface (the metaset command) or the Enhanced Storage tool within the Solaris Management Console.

After drives are added to a disk set, the disk set can be reserved (or taken) and released by hosts in the disk set. When a disk set is reserved by a host, the other host in the disk set cannot access the data on the drives in the disk set. To perform maintenance on a disk set, a host must be the owner of the disk set or have reserved the disk set. A host takes implicit ownership of the disk set by putting the first drives into the set.

Reserving a Disk Set

Before a host can use drives in a disk set, the host must reserve the disk set. There are two methods of reserving a disk set:

• Safely - When you safely reserve a disk set, Solaris Volume Manager attempts to take the disk set, and the other host attempts to release the disk set. The release (and therefore the reservation) might fail.

• Forcibly - When you forcibly reserve a disk set, Solaris Volume Manager reserves the disk set whether or not another host currently has the set reserved. This method is generally used when a host in the disk set is down or not communicating. All disks within the disk set are taken over. The state database is read in on the host performing the reservation and the shared volumes configured in the disk set become accessible. If the other host had the disk set reserved at this point, it would panic due to reservation loss.

  Normally, two hosts in a disk set cooperate with each other to ensure that drives in a disk set are reserved by only one host at a time. A normal situation is defined as both hosts being up and communicating with each other.

If a drive has been determined unexpectedly not to be reserved (perhaps because another host using the disk set forcibly took the drive), the host will panic. This behavior helps to minimize data loss which would occur if two hosts were to simultaneously access the same drive.

For more information about taking or reserving a disk set, see How to Take a Disk Set.

Releasing a Disk Set

Releasing a disk set can be useful when you perform maintenance on the physical drives in the disk set. When a disk set is released, it cannot be accessed by the host. If both hosts in a disk set release the set, neither host in the disk set can access the drives in the disk set.

For more information about releasing a disk set, see How to Release a Disk Set.