Disks that can be connected to more than one Solaris host at a time are multihost devices. In the Sun Cluster environment, multihost storage makes disks highly available. Sun Cluster software requires multihost storage for two-host clusters to establish quorum. Greater than two-host clusters do not require quorum devices. For more information about quorum, see Quorum and Quorum Devices.
Multihost devices have the following characteristics.
Tolerance of single-host failures.
Ability to store application data, application binaries, and configuration files.
Protection against host failures. If clients request the data through one host and the host fails, the requests are switched over to use another host with a direct connection to the same disks.
Global access through a primary host that “masters” the disks, or direct concurrent access through local paths. The only application that uses direct concurrent access currently is Oracle Real Application Clusters Guard.
A volume manager provides for mirrored or RAID-5 configurations for data redundancy of the multihost devices. Currently, Sun Cluster supports Solaris Volume Manager and Veritas Volume Manager as volume managers, and the RDAC RAID-5 hardware controller on several hardware RAID platforms.
Combining multihost devices with disk mirroring and disk striping protects against both host failure and individual disk failure.
See Chapter 4, Frequently Asked Questions for questions and answers about multihost storage.