Administering Disksets

Disksets must be created and configured using the DiskSuite command line interface (the metaset(1M) command). After you have created a diskset, you can administer state database replicas, metadevices, and hot spare pools within a diskset using either DiskSuite Tool or the command line utilities.

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

The SCSI reserve command is issued to each drive in the diskset to reserve it for exclusive use by the current host. Each drive in the diskset is probed once every second to determine that it is still reserved.

If a drive has been determined unexpectedly not to be reserved, the host will panic. This behavior helps to minimize data loss which would occur if two hosts were to simultaneously access the same drive.

Reserving a Diskset

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

• Safely - When you safely reserve a diskset, DiskSuite checks to see if another host currently has the set reserved. If another host has the diskset reserved, your host will not be allowed to reserve the set.

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

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

Releasing a Diskset

Sometimes it may be desirable to release a diskset. Releasing a diskset can be useful when performing maintenance on the drives in the set. When a diskset is released, it cannot be accessed by the host. If both hosts in a diskset release the set, neither host in the diskset can access the drives in the set.