Use the Setting a Quorum Disk panel in the SAN Volume Controller Console to
identify the selected managed disk (MDisk) as a quorum disk.
Introduction
A quorum is
set of nodes that operates as a cluster. Each node has a connection
to every other node in the cluster. If a connection failure causes
the cluster to split into two or more groups of nodes that have full
connection within the group, the quorum is the group that is selected
to operate as the cluster. The cluster supports three MDisks as quorum
disk candidates. Each disk is assigned an number, either 0, 1, or
2, called a quorum index, that identifies the MDisk as a quorum disk
to the cluster. You can also assign one of the quorum disks to be
the active quorum disk, which is used to resolve a tie-break situation.
There can only be one active quorum disk at a time.
You must set quorum disks on
multiple controllers to avoid the possibility of losing all of the
quorum disks with a single failure. Mirrored virtual disks (VDisks)
also are taken offline when all the quorum disks are on a single controller
that experiences a failure. Mirrored VDisks are taken offline because
synchronization data is stored on the quorum disks. To protect against
mirrored VDisks being taken offline, follow these guidelines for changing
the managed disks that are assigned as quorum disk candidates:
- When possible, distribute the quorum candidate disks so that each
MDisk is provided by a different storage system.
- Ensure that the status of the MDisk that is being set as a quorum
disk is online before setting it as the quorum disk.
- Wait at least two minutes between setting quorum disks. This delay
allows time for the update to the quorum disk to complete before setting
another quorum disk.
Note: If any controller that is associated with an MDisk
shows the Allow Quorum attribute set to false, the set
quorum action fails for that MDisk. To determine the current setting
for the Allow Quorum attribute for the controller that is associated
with the MDisk, select and select
the name of the disk controller to view details about the controller.
For a list of controllers that support quorum, see the following Web
site:
Support for SAN Volume Controller (2145)
Web site
Fields
You
can update the following fields:
- Quorum Index
- Select the quorum index number for the selected MDisk. The number
can be either: 0, 1 or 2.
- Set as the Active Quorum Disk
- Select this option to set the selected MDisk to be the active
quorum disk. The active quorum disk is the disk which is used first
in the event of a cluster partition. You should set an active quorum
disk when nodes in an I/O group are split between different physical
locations to ensure that the most highly-available quorum disk is
used.
Attention: You must set quorum disks on
multiple controllers to avoid the possibility of losing all of the
quorum disks with a single failure.
Actions
The
following actions are available:
- OK
- Click this button to set quorum disk.
- Cancel
- Click this button to exit the panel without setting a quorum disk.