Heartbeats; Virtual Servers; Failover - HP Rx2620-2 - Integrity - 0 MB RAM Installation And Configuration Manual

In the case of a failure or split-brain, all partitions that do not contain an MNS quorum are
terminated. This ensures that if there is a partition running that contains a majority of the nodes,
it can safely start up any resources that are not running on that partition. Thus, it can be the only
partition in the cluster that is running resources.
MNS quorums have strict requirements to ensure they work correctly. Be sure that you fully
understand the issues involved in using MNS-based clusters before implementing this solution.
Use MNS quorums only in the following situations:
Geographically dispersed clusters
Clusters with no shared disks

Heartbeats

Heartbeats are network packets periodically broadcast by each node over the private cluster
network. Heartbeats inform other nodes of a single system's health, configuration, and network
connection status. When heartbeat messages are not received among the other nodes as expected,
the cluster service interprets this as node failure, and a failover begins.

Virtual Servers

Groups that contain an IP address resource and a network name resource (along with other
resources) are published to clients on the network under a unique server name. Because these
groups appear as individual servers to clients, they are called virtual servers. Users access
applications or services on a virtual server the same way they access applications or services on
a physical server. They do not need to know that they are connecting to a cluster and have no
knowledge of which node they are connected to.

Failover

Failover is the process of moving a group of resources from one node to another in the case of a
failure. For example, in a cluster where Microsoft Internet Information Server (IIS) is running on
node A and node A fails, IIS fails over to node B of the cluster.
18 Introduction
A single MSCS cluster has members in multiple geographic
sites. Though geographic clusters can use a standard
quorum, presenting the quorum as a single, logical shared
drive among all sites can be challenging. MNS quorums
solve these challenges by enabling the quorum to be stored
on the local hard disk.
NOTE:
HP supports geographically dispersed clusters
with shared quorums using Cluster Extension XP (CLX)
and Continuous Access (CA) technology on XP storage
products.
Some specialized configurations need tightly consistent
cluster features without having sharing disks. For example:
• Clusters that host applications that can failover, but
where another, application-specific method can keep
data consistent between nodes (for example, database
log shipping for keeping the database state up-to-date,
or file replication for static data).
• Clusters that host applications that have no persistent
data but must cooperate in a tightly coupled way to
provide a consistent volatile state.
• Independent Software Vendors (ISVs): By abstracting
storage from the cluster service, an MNS quorum
provides ISVs with greater flexibility to design
sophisticated cluster scenarios.