Dell PS4100 Technical Information download pdf (Page 34)

June 2012 Dell EqualLogic Configuration Guide v13.2 28

3.8 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 13 provides definitions of EqualLogic PS Series terminology related to replication processing.

Table 13 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.

3.8.1 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.

• PS series groups can have up to 16 replication partners and can support a maximum of 10,000

total snapshots and replicas from all of its replication partners.

• A group can have volumes replicating with multiple partners, but

an individual volume can

have only one replication partner

• A maximum of 256 volumes per group can be configured for active replication.

• All volumes that are part of a volume collection can only replicate with a single partner.

• A volume can have up to a maximum of 512 replicas stored on a partner group.

o For a PS4000 only group, you cannot exceed two replication partners and 32 volumes

configured for replication

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