Designing Disaster Recovery Clusters using Metroclusters and Continentalclusters, Reprinted October 2011 (5900-1881)

Table 8 Serviceguard and Continentalclusters Commands (continued)
How the commands work in ContinentalclustersHow the commands
work in Serviceguard
Commands
Will not re-enable switching on a recovery package if any of the primary,
data receiver, or data sender package in the same recovery group is
halts a node in a
highly available
cluster
cmhaltnode -f
running or enabled. Will not re-enable a primary, data receiver, or data
sender package if the recovery package in the same recovery group is
running or enabled.
Will not re-enable switching on a recovery package if any of the primary,
data receiver, or data sender package in the same recovery group is
This command will halt
daemons on all
cmhaltcl -f
running or enabled. Will not re-enable a primary, data receiver, or datacurrently running
systems sender package if the recovery package in the same recovery group is
running or enabled.
Designing a Disaster Recovery Architecture for use with Continentalclusters
A recovery pair in Continentalclusters consists of two Serviceguard clusters. One functions as a
primary cluster and the other functions as recovery cluster for a specific application. Prior to
Continentalclusters version A.05.00, one recovery pair can be configured in Continentalclusters.
Starting with Continentalclusters version A.05.00, a configuration of multiple recovery pairs is
allowed.
In the multiple recovery pair configuration, more than one primary cluster (where the primary
packages are running) can be configured to share the same recovery cluster (where the recovery
package is running).
The key elements providing disaster tolerance in Continentalclusters recovery pair are:
• Mutual Recovery
• Serviceguard clusters
• Data replication
• Highly available WAN networking
• Data center processes and procedures coordinated between the two cluster sites
There is significant amount of latitude in selecting these elements for a configuration. It is
recommended the choices are recorded on worksheets which can be reviewed and updated
periodically.
Mutual Recovery
For mutual recovery, any cluster in Continentalclusters recovery pair may contain both primary
and recovery packages for any recovery group. Recovery groups may be defined, for example,
such that cluster A and cluster B contain recovery packages. In this case, cmrecovercl could be
run on cluster B to recover packages from cluster A, or on cluster A to recover packages from
cluster B.
Serviceguard Clusters
Each Serviceguard cluster in Continentalclusters provides high availability for an application at
the local level at that particular site. For optimal performance and to assure adequate capacity on
the recovery cluster, it is best to have similar hardware on both clusters. For example, if one cluster
contains two systems with 1Gb of memory each, it is not a good idea to have a low-end system
with 128 Mb of memory in the other cluster. Each cluster may have as many nodes as are permitted
in an ordinary Serviceguard cluster, and each may be running packages that are not configured
to fail over between clusters.
48 Designing Continentalclusters