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7 PS Series Asynchronous Replication Best Practices and Sizing Guide | BP1012
2 Asynchronous replication overview
PS Series asynchronous replication is used to replicate volumes between different groups as a way to protect
against data loss. The two groups must be connected through a TCP/IP-based network. This means that the
physical distance between the groups is not limited. The replication partner group can be located in the same
data center, or it can be in a remote location. In practice, the actual bandwidth and latency characteristics of
the network connection between replication groups must be able to support the amount of data that needs to
be replicated and the time window in which replication needs to occur.
IT administrators can enable replication through the Group Manager GUI or the Group Manager CLI. Once
enabled, volume replication functions can be managed using the GUI, the CLI, or Auto-Snapshot Manager
(ASM) tools. ASM tools are included as part of the Host Integration Tools for Microsoft
®
. VMware
®
also has
similar Host Integration Tools known as Virtual Storage Manager (VSM). A replica can be created from a
single volume or a volume collection. A volume collection allows up to eight volumes to be grouped together
so that the replication process for that collection can be managed as if it was a single volume. This is useful
when replicating multiple volumes that belong to the same application.
Asynchronous replication initially creates a copy on a secondary storage system, and then synchronizes the
changed data to the replica copy. A replica represents the contents of a volume at a point in time at which the
replica was created. This type of replication is often referred to as point-in-time replication because the replica
copies the state of the volume at time the replication is initiated. The frequency in which replication occurs
determines how old the replica becomes relative to the current state of the source volume.
2.1 Terminology
This document uses the following PS Series terminology:
Terminology
Term
Description
Asynchronous
replication
The built-in replication feature included with every PS Series array.
Replica
A point-in-time synchronized copy of a PS Series volume stored in a
secondary group.
Replica set
A collection of all point-in-time synchronized replicas for a specific source
volume.
Pool
A pool is a storage space that each member (array) is assigned to after being
added to a group. A group may have up to four pools, and a pool may have
up to 8 members
1
.
Group
A group consists of one or more PS-Series arrays connected to an IP
network that work together to provide SAN resources to servers. A group
may contain up to 16 members
2
and is managed as a single storage entity.
Primary group
A group containing the source volume(s) to be copied or replicated.
Source group
Same as primary group.