Dell PowerVault MD3260i - Manual (Page 95)

8
Using The Remote Replication (Legacy) Premium
Feature
The Remote Replication (legacy) 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. Remote Replication (legacy) is designed for
extended storage environments in which the storage arrays that are used for Remote Replication (legacy) are
maintained at separate sites. Virtual disks on one storage array are replicated to virtual disks 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 replicated pair. The data transfers occur at Fibre Channel speeds to maintain data on the different storage
arrays. Because Remote Replication (legacy) is storage based, it does not require any server overhead or application
overhead.
You can use Remote Replication (legacy) for these functions:
Disaster recovery Remote Replication (legacy) 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
replicated 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 Remote Replication (legacy) 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 Remote Replication (legacy) provides the ability to have two storage arrays back up each other
by duplicating critical virtual disks on each storage array to virtual disks 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 Remote Replication (Legacy) Works
When you create a remote replicated pair, the remote replicated pair consists of a primary virtual disk on a local storage
array and a secondary virtual disk on a storage array at another site. A standard virtual disk might only be included in
one replicated virtual disk pair.
The primary virtual disk is the virtual disk that accepts host I/O activity and stores application data. When the replication
relationship is first created, data from the primary virtual disk is copied in its entirety to the secondary virtual disk. This
process is known as a full synchronization and is directed by the RAID controller module owner of the primary virtual
disk. During a full synchronization, the primary virtual disk remains fully accessible for all normal I/O operations.
The RAID controller module owner of the primary virtual disk initiates remote writes to the secondary virtual disk to keep
the data on the two virtual disks synchronized.
The secondary virtual disk maintains a replication (or copy) of the data on its associated primary virtual disk. The RAID
controller module owner of the secondary virtual disk receives remote writes from the RAID controller module owner of
the primary virtual disk but will not accept host write requests. Hosts are able to read from the secondary virtual disk,
which appears as read-only.
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