Single Quorum; Single Quorum Example - HP Rx2620-2 - Integrity - 0 MB RAM Installation And Configuration Manual

Arbitration
There are two types quorums: the single quorum and the Majority Node Set (MNS) quorum.
Single quorum clusters behave differently than MNS quorum clusters, so take care when choosing
a model for your cluster.
For example, if you have only two nodes in your cluster, the MNS model is not recommended
because failure of one node leads to failure of the entire cluster (a majority of nodes is impossible).
After the cluster is created, you cannot change the quorum from one type to another.

Single Quorum

A single quorum uses a quorum log file located on a single disk hosted on a shared storage
interconnect that is accessible by all nodes in the cluster. Single quorums are available in Windows
Server 2003 Enterprise Edition and Datacenter Edition.
IMPORTANT:
because the entire physical disk resource is moved during failover.
NOTE:
You can configure clusters to use the local hard disk on one node to store the quorum,
but this is only supported for testing and development purposes. Do not use this configuration
in a production environment. Each node connects to the shared storage through some type of
interconnect, with the storage consisting of either external hard disks (usually configured as
RAID disks), or a storage area network (SAN), where logical slices of the SAN are presented as
physical disks.
The following figure shows a single quorum in a four-node cluster.
Figure 1-2 Single Quorum Example
Single quorums are sufficient for most clusters. The following are typical single quorum situations:
Highly available data in a single
location
16 Introduction
The quorum is used as the tie-breaker to avoid split-brain scenarios. A
split-brain scenario occurs when all network communication links between
two or more cluster nodes fail. In these cases, the cluster can split into two or
more partitions that cannot communicate with each other. The quorum then
guarantees that any cluster resource is brought online on one node only. It
does this by allowing the partition that owns the quorum to continue, while
the other partitions are evicted from the cluster.
The quorum must use a physical disk resource, as opposed to a disk partition,
Most customers that require their data to be highly
available need this on a per-site basis only. If they have
multiple sites, each site has its own cluster. Typical
applications that use this type of cluster include Microsoft
SQL Server, file shares, printer queues, and network
services (for example, DHCP and WINS).