March 2013
Dell EqualLogic Configuration Guide v14.1
6-42
6
Array firmware features
6.1
Replication
Replication is a powerful feature that can help you manage and implement a disaster recovery strategy
for your business applications and data. By replicating business-critical volumes, you ensure that your
business operations can resume quickly on a partner group in the event of a disaster on the primary
group. You also have the ability to restore the configuration to its original state if the problem on the
original group can be corrected. The replication process does not require placing volumes offline.
Thus you can take advantage of the benefits of replication without causing interruption in application
or data availability.
In EqualLogic PS Series storage, replication is the process of copying volume data from one PS Series
group to another PS Series group. Physical distance between the replication groups is not a concern
as long as they are connected by a reliable TCP/IP network path.
Table 19 provides definitions of EqualLogic PS Series terminology related to replication processing.
Table 19
Replication terminology
Term
Description
Replica
A time synchronized copy of an EqualLogic volume stored in a
Secondary Group.
Replica Set
A collection of all time synchronized replicas for a specific source
volume.
Primary Group
A group containing the source volume(s) to be copied or
replicated.
Source Group
Same as “Primary Group”.
Secondary Group
A group containing the replica or copy of the source volume(s).
Destination Group
Same as “Secondary Group”.
Delegated Space
The amount of space on the secondary group that is “delegated”
to a replication partner, to be reserved for retaining replicas.
Replica Reserve
The space allocated from delegated space in the secondary group
to store the volume replica set for a specific volume.
Local Reserve
The amount of space reserved on the local or Primary Group for
holding temporary snapshots and failback snapshots of the
source volume.
6.1.1
Replication limits
You need to consider the following limits when designing a volume replication topology:
•
A primary group can replicate to multiple partner (secondary) replica groups.
