HP Serviceguard Extended Distance Cluster for Linux A.12.00.00 Deployment Guide, March 2014

nodes in an extended distance cluster is set by the limits of the data replication technology and
networking limits. An extended distance cluster is shown in Figure 3.
NOTE: There are no rules or recommendations on how far the third location must be from the
two main data centers. The third location can be as close as the room next door with its own power
source or can be as far as in a site across town. The distance among all three locations dictates
the level of disaster recovery an extended distance cluster can provide.
1.3.2 Metrocluster
A metropolitan cluster is a cluster that has alternate nodes located in two different parts of a city
or in adjacent cities. Putting nodes further apart increases the likelihood that alternate nodes will
be available for failover in the event of a disaster. For more information about Metrocluster, see
the Understanding and Designing Serviceguard Disaster Recovery Architectures at http://
www.hp.com/go/linux-serviceguard-docs.
1.3.3 Continental Cluster
A continental cluster provides an alternative disaster recovery solution in which distinct clusters
can be separated by large distances, with wide area networking used between them. For more
information about Continental Cluster, see the Understanding and Designing Serviceguard Disaster
Recovery Architectures at http://www.hp.com/go/linux-serviceguard-docs.
1.4 Managing a Disaster Recovery Solutions
In addition to the changes in hardware and software to create a disaster recovery architecture,
there are also changes in the way you manage the environment. Configuration of a disaster
recovery architecture needs to be carefully planned, implemented and maintained. There are
additional resources needed, and additional decisions to make concerning the maintenance of a
disaster recovery architecture:
• Manage it in-house, or hire a service?
Hiring a service can remove the burden of maintaining the capital equipment needed to
recover from a disaster. Most disaster recovery services provide their own off-site equipment,
which reduces maintenance costs. Often the disaster recovery site and equipment are shared
by many companies, further reducing cost.
Managing disaster recovery in-house gives complete control over the type of redundant
equipment used and the methods used to recover from disaster, giving you complete control
over all means of recovery.
• Implement automated or manual recovery?
Manual recovery costs less to implement and gives more flexibility in making decisions while
recovering from a disaster. Evaluating the data and making decisions can add to recovery
time, but it is justified in some situations, for example if applications compete for resources
following a disaster and one of them has to be halted.
Automated recovery reduces the amount of time and in most cases eliminates human intervention
needed to recover from a disaster. You may want to automate recovery for any number of
reasons:
◦ Automated recovery is usually faster.
◦ Staff may not be available for manual recovery, as is the case with “lights-out” data
centers.
12 Disaster Recovery in a Serviceguard Cluster