Background Information for Disk Sets

When working with disk sets, consider the following Background Information for Disk Sets and Administering Disk Sets.

Requirements for Disk Sets

• Solaris Volume Manager must be configured on each host that will be connected to the disk set.

• Each host must have its local state database set up before you can create disk sets.

• To create and work with a disk set in a clustering environment, root must be a member of Group 14, or the /.rhosts file must contain an entry for the other host name (on each host).

• 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.)

• You cannot add a drive that is in use to a disk set. Before you add 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 disk set. The process of adding the disk to the disk set repartitions the disk and destroys existing data.

• All disks that you plan to share between hosts in the disk set must be connected to each host and must have the exact same path, driver, and name on each host. Specifically, a shared disk drive must be seen on both hosts at the same device number (c#t#d#). If the numbers are not the same on both hosts, you will see the message “drive c#t#d# is not common with host xxx” when attempting to add drives to the disk set. The shared disks must use the same driver name (ssd). See How to Add Drives to a Disk Set for more information on setting up shared disk drives in a disk set.

Guidelines for Disk Sets

• The default total number of disk sets on a system is 4. You can increase this value up to 32 by editing the /kernel/drv/md.conf file, as described in How to Increase the Number of Default Disk Sets. The number of shared disk sets is always one less than the md_nsets value, because the local set is included in md_nsets.

• Unlike local volume administration, it is not necessary to create or delete state database replicas manually on the disk set. Solaris Volume Manager tries to balance a reasonable number of replicas across all drives in a disk set.

• When drives are added to a disk set, Solaris Volume Manager re-balances the state database replicas across the remaining drives. Later, if necessary, you can change the replica layout with the metadb command.