HP 3PAR Geocluster Software - Manual (Page 9)

3PAR GeoCluster 1.0.0.14 for Windows User’s Guide
320-200263 Page 9
2.1.1 Microsoft Cluster Server
Microsoft Cluster Server revolves around the active/passive clustering of several Windows
servers, called nodes. The cluster structure allows single resources to be shared by all the
nodes, with typically only one node, the owner node being able to access these at a given
time. Clustering also allows failover capability, which ensures continuity of service in case
one or more nodes experience problems by making sure the owner role is transferred to a
functional node.
MSCS avoids split-brain scenarios, where, in case of communication failure, each node is
likely to conclude being the active one, resulting in simultaneous resource access and data
corruption, using specific methods. Among those methods, 3PAR GeoCluster for Windows
supports the following:

Majority Node Set, which, in order to be ideally configured, requires an odd number
of servers. In case of failure, the new owner node can only be selected from nodes
able to perceive at least 50% of the total number of nodes, plus themselves. Nodes
not meeting this requirement at any time will exclude themselves from the cluster.
The odd node can be located remotely from all the other nodes and is traditionally
named “Quorum”.

Majority Node Set with File Share, which instead of the odd node configuration
makes a shared storage space that hosts a file called the file share witness accessible
to all the nodes.
Locating nodes on sites geographically remote from each other further ensures continuity
of service by protecting the cluster against site failure. However, the implementation of
remote sites has its own specific constraints. This design is called metropolitan clusters or
geographically dispersed clusters.