Guidelines for Mirroring Multihost Disks

To mirror all multihost disks in a Sun Cluster configuration enables the configuration to tolerate single-disk failures. Sun Cluster software requires that you mirror all multihost disks across disk expansion units. You do not need to use software mirroring if the storage device provides hardware RAID as well as redundant paths to disks.

Consider the following points when you mirror multihost disks.

• Separate disk expansion units – Each submirror of a given mirror or plex should reside in a different multihost disk-expansion unit.

• Disk space – Mirroring doubles the amount of necessary disk space.

• Three-way mirroring – Solstice DiskSuite/Solaris Volume Manager software and VERITAS Volume Manager (VxVM) support three-way mirroring. However, Sun Cluster software requires only two-way mirroring.

• Number of metadevices or volumes – Under Solstice DiskSuite/Solaris Volume Manager software, mirrors consist of other Solstice DiskSuite metadevices or Solaris Volume Manager volumes such as concatenations or stripes. Large configurations might contain a large number of metadevices or volumes.

• Differing disk sizes – If you mirror to a disk of a different size, your mirror capacity is limited to the size of the smallest submirror or plex.

For more information about multihost disks, see the Sun Cluster 3.1 10/03 Concepts Guide.