Chapter 8. About Enhanced Remote Mirroring Premium Feature; How Enhanced Remote Mirroring Works - IBM System Storage DS3000 Programming Manual

Chapter 8. About Enhanced Remote Mirroring premium
feature
The Enhanced Remote Mirroring premium feature provides for online, real-time replication of data
between storage subsystems over a remote distance. In the event of a disaster or a catastrophic failure on
one storage subsystem, you can promote the second storage subsystem to take over responsibility for
computing services. Enhanced Remote Mirroring is designed for extended storage environments in which
the storage subsystems that are used for Enhanced Remote Mirroring are maintained at separate sites.
Logical drives on one storage subsystem are mirrored to logical drives on another storage subsystem
across a fabric SAN. Data transfers can be synchronous or asynchronous. You choose the method when
you set up the remote-mirror pair. The data transfers occur at Fibre Channel speeds to maintain data on
the different storage subsystems. Because Enhanced Remote Mirroring is storage based, it does not
require any server overhead or application overhead.
You can use Enhanced Remote Mirroring for these functions:
Disaster recovery – Enhanced Remote Mirroring lets you replicate data from one site to another site,
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which provides an exact mirror duplicate at the remote (secondary) site. If the primary site fails, you
can use mirrored data at the remote site for failover and recovery. You can then shift storage operations
to the remote site for continued operation of all of the services that are usually provided by the
primary site.
Data vaulting and data availability – Enhanced Remote Mirroring lets you send data off site where it
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can be protected. You can then use the off site copy for testing or to act as a source for a full backup to
avoid interrupting operations at the primary site.
Two-way data protection – Enhanced Remote Mirroring provides the ability to have two storage
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subsystems back up each other by mirroring critical logical drives on each storage subsystem to logical
drives on the other storage subsystem. This action lets each storage subsystem recover data from the
other storage subsystem in the event of any service interruptions.

How Enhanced Remote Mirroring Works

When you create a remote-mirror pair, the remote-mirror pair consists of a primary logical drive on a local
storage subsystem and a secondary logical drive on a storage subsystem at another site. A standard logical
drive might only be included in one mirrored logical drive pair.
Note: Enhanced Remote Mirroring is not supported in DS3000 storage subsystem configurations.
Table 8-1. Maximum Number of Defined Mirrors
Controller Model
DS3500 series
DCS3700
DCS3700 storage subsystem with
Performance Module Controllers
DS3950
DS4300
DS4400
DS4500
DS4700
© Copyright IBM Corp. 2008, 2012
Maximum Number of Defined
Mirrors
8 (16 with controller firmware 7.77
and later)
16
16
64
32
64
64
64
8-1