Dell AX4-5 - Manual (Page 32)

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Preparing Your Systems for Clustering
Configuring the Quorum Disk in Failover Clustering
The Quorum configuration determines the maximum number of failures a
Failover Cluster can sustain without stopping the Cluster Service. In your
cluster configured with the Windows Server 2008 operating system, you do
not have to configure a shared storage resource for the Quorum disk. The
following terms are commonly used in the concept of Quorum resource in the
Windows Server 2008 operating system:
• The Quorum disk in the Failover Cluster must have the votes from a
majority of nodes in the cluster
• Depending on the quorum configuration you select, the term failure may
refer to the failure of a node, failure of a disk designated as the witness, or
the failure of a file share designated as the witness.
Failover clustering provides the following four options for quorum
configuration:
1 Node and Disk Majority - The cluster nodes, along with a disk resource on
shared storage that is designated as a witness, are given one vote each. The
cluster is online even if half of the total number of nodes rounded up are
alive and the witness disk is online. If the witness disk fails, the cluster can
sustain the failure of one node less than half of the total number of nodes
rounded up.
If N denotes the number of nodes in your cluster which have one vote each
and one vote is allotted to the witness disk, then, the total number of votes
for the cluster to be up:
{N+1 (witness disk) +1}/2
NOTE:
If your cluster has odd number of Cluster Nodes, truncate the decimal
output to the next whole number. For example, if your cluster has 5 nodes,
then the total number of votes for the cluster is 5+1+1= 7/2 = 3.5. Round off 3.5
to next whole number which is 4. Therefore, the total number of votes required
for the cluster to be online is 4.
2 Node and File Share Majority - This model is similar to Node and Disk
Majority in behavior but the witness disk is replaced by a File share to act
as the witness. You can configure the File Share Witness as any network
share that is accessible by all the cluster nodes.