Preliminary Information for Creating Disksets

• A diskset is a set of shared disk drives containing DiskSuite objects that can be shared exclusively (but not concurrently) by one or two hosts. Disksets are enablers for host fail-over scenarios.

• DiskSuite must be installed on each host that will be connected to the diskset.

• There is one metadevice state database per shared diskset and one on the "local" diskset. Each host must have its local metadevice state database set up before you can create disksets.

• Unlike local metadevice administration, it is not necessary to create or delete state database replicas manually on the diskset. DiskSuite tries to balance a reasonable number of replicas across all drives in a diskset.

• Each host in a diskset must have a local diskset that is separate from the shared diskset. The local diskset for a host consists of all drives that are not part of a shared diskset.

• All disks that you plan to share between hosts in the diskset must be connected to each host and must have the same name on each host. Configuring the hardware for use in diskset configuration can be problematic. The disk drives must be symmetric; that is, the shared drives must have the same device number, which implies the same device name/number (controller/target/drive). See "How to Configure Disk Drive Device Names for a Diskset (Command Line)".

• You can create a diskset with one host and add the second host later.

• You cannot add a drive that is in use to a diskset. Before adding a drive, make sure it is not currently being used for a file system, database, or any other application.

• Do not add a drive with existing data that you want to preserve to a diskset; the process of adding it to the diskset repartitions the disk, destroying any data.

• When a drive is accepted into a diskset, DiskSuite repartitions it so that the metadevice state database replica for the diskset can be placed on the drive. Drives are repartitioned when they are added to a diskset only if Slice 7 is not set up correctly. A small portion of each drive is reserved in Slice 7 for use by DiskSuite. The remainder of the space on each drive is placed into Slice 0. Any existing data on the disks is lost by the repartitioning. After adding a drive to a diskset, it may be repartitioned as necessary, with the exception that Slice 7 is not altered in any way. If Slice 7 starts at cylinder 0, and is large enough to contain a state database replica, the disk is not repartitioned.

• When drives are added to a diskset, DiskSuite re-balances the state database replicas across the remaining drives. Later, if necessary, you can change the replica layout with the metadb(1M) command.

• To create a diskset, root must be a member of Group 14, or the ./rhosts file must contain an entry for the other hostname (on each host).

Disksets must be created and configured using the DiskSuite command line interface. 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.