Sun Cluster configurations use quorum devices to maintain data and resource integrity. If the cluster temporarily loses connection to a voting node, the quorum device prevents amnesia or split-brain problems when the voting cluster node attempts to rejoin the cluster. For more information about the purpose and function of quorum devices, see Quorum and Quorum Devices in Sun Cluster Concepts Guide for Solaris OS.
During Sun Cluster installation of a two-host cluster, you can choose to let the scinstall utility automatically configure as a quorum device an available shared disk in the configuration. Shared disks include any Sun NAS device that is configured for use as a shared disk. The scinstall utility assumes that all available shared disks are supported as quorum devices.
If you want to use a quorum server or a Network Appliance NAS device as the quorum device, you configure it after scinstall processing is completed.
After installation, you can also configure additional quorum devices by using the clsetup(1CL) utility.
You do not need to configure quorum devices for a single-host cluster.
If your cluster configuration includes third-party shared storage devices that are not supported for use as quorum devices, you must use the clsetup utility to configure quorum manually.
Consider the following points when you plan quorum devices.
Minimum – A two-host cluster must have at least one quorum device, which can be a shared disk, a quorum server, or a NAS device. For other topologies, quorum devices are optional.
Odd-number rule – If more than one quorum device is configured in a two-host cluster, or in a pair of hosts directly connected to the quorum device, configure an odd number of quorum devices. This configuration ensures that the quorum devices have completely independent failure pathways.
Distribution of quorum votes – For highest availability of the cluster, ensure that the total number of votes that are contributed by quorum devices is less than the total number of votes that are contributed by voting nodes. Otherwise, the nodes cannot form a cluster if all quorum devices are unavailable, even if all nodes are functioning.
Connection – You must connect a quorum device to at least two voting nodes.
SCSI fencing protocol – When a SCSI shared-disk quorum device is configured, its fencing protocol is automatically set to SCSI-2 in a two-host cluster or SCSI-3 in a cluster with three or more voting nodes.
Changing the fencing protocol of quorum devices – For SCSI disks that are configured as a quorum device, you must unconfigure the quorum device before you can enable or disable its SCSI fencing protocol.
Software quorum protocol – You can configure supported shared disks that do not support SCSI protocol, such as SATA disks, as quorum devices. You must disable fencing for such disks. The disks would then use software quorum protocol, which emulates SCSI PGR.
The software quorum protocol would also be used by SCSI shared disks if fencing is disabled for such disks.
ZFS storage pools – Do not add a configured quorum device to a ZFS storage pool. When a configured quorum device is added to a ZFS storage pool, the disk is relabeled as an EFI disk and quorum configuration information is lost. The disk can then no longer provide a quorum vote to the cluster.
After a disk is in a storage pool, you can configure that disk as a quorum device. Or, you can unconfigure the quorum device, add it to the storage pool, then reconfigure the disk as a quorum device.
For more information about quorum devices, see Quorum and Quorum Devices in Sun Cluster Concepts Guide for Solaris OS and Quorum Devices in Sun Cluster Overview for Solaris OS.