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Chapter 8: Using the Synchronous Mirroring Premium Feature 141
8
Using the Synchronous Mirroring Premium Feature
The Synchronous Mirroring premium feature provides for online, real-time
replication of data between storage arrays over a remote distance. In the event of a
disaster or a catastrophic failure on one storage array, you can promote the second
storage array to take over responsibility for computing services. Synchronous
Mirroring is designed for extended storage environments in which the storage arrays
that are used for Synchronous Mirroring are maintained at separate sites. Volumes on
one storage array are mirrored to volumes on another storage array across a fabric
SAN. Data transfers can be synchronous or asynchronous. You choose the method
when you set up the remote mirrored pair. The data transfers occur at Fibre Channel
speeds to maintain data on the different storage arrays. Because Synchronous
Mirroring is storage based, it does not require any server overhead or application
overhead.
You can use Synchronous Mirroring for these functions:

Disaster recovery
– Synchronous Mirroring lets you replicate data from one site
to another site, which provides an exact 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
– Synchronous Mirroring lets you send data
off site where it 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
– Synchronous Mirroring provides the ability to have
two storage arrays back up each other by duplicating critical volumes on each
storage array to volumes on the other storage array. This action lets each storage
array recover data from the other storage array in the event of any service
interruptions.
How
Synchronous
Mirroring Works When you create a remote-mirror pair, the remote-mirror pair consists of a
primary
volume
on a local storage array and a
secondary volume
on a storage array at another
site. A standard volume might only be included in one mirrored volume pair.