LUNs that can be connected to more than one cluster node at a time are multihost devices. Greater than two-node clusters do not require quorum devices. A quorum device is a shared storage device or quorum server that is shared by two or more nodes and that contributes votes that are used to establish a quorum. The cluster can operate only when a quorum of votes is available. For more information about quorum and quorum devices, see Quorum and Quorum Devices.
Multihost devices have the following characteristics:
Ability to store application data, application binaries, and configuration files.
Protection against host failures. If clients request the data through one node and the node fails, the I/O requests are handled by the surviving node.
A volume manager can provide software RAID protection for the data residing on the multihost devices.
Combining multihost devices with disk mirroring protects against individual disk failure.