To mirror all multihost disks in a Sun Cluster configuration enables the configuration to tolerate single-device failures. Sun Cluster software requires that you mirror all multihost disks across expansion units. You do not need to use software mirroring if the storage device provides hardware RAID as well as redundant paths to devices.
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 expansion unit.
Disk space – Mirroring doubles the amount of necessary disk space.
For more information about multihost disks, see Multihost Disk Storage in Sun Cluster Overview for Solaris OS and Sun Cluster Concepts Guide for Solaris OS.