Dell PowerVault MD3820f - Manual (Page 208)

Types Of Remote Replication
The following are the types of Remote Replication premium features supported on your storage array:
• Remote Replication — Also known as standard or asynchronous, it is supported on both iSCSI- and
Fibre Channel-based storage arrays (both local and remote storage arrays must use the same data
protocol) and requires a dual RAID controller configuration.
• Remote Replication (Legacy) — Also known as synchronous or full-write, it is supported on Fibre
Channel storage arrays only.
Differences Between Remote Replication Features
As compared to the (synchronous) Remote Replication (Legacy) feature, the standard (asynchronous
write) Remote Replication premium feature uses a point-in-time snapshot image to capture the state of
the source virtual disk and only writes data that has changed since the last point-in-time image.
With standard Remote Replication, the remote storage array is not fully synchronized with the local
storage array. As a result, in the event of a sudden, total loss of the remote storage array, some
transactions could be lost.
With synchronous Remote Replication (Legacy), every data write to a source virtual disk is replicated to a
remote virtual disk. This produces an identical, real-time remote of production data.
Other differences include:
• Number of repository virtual disk required — Standard Remote Replication requires a repository virtual
disk to be created for each replicated pair (remote virtual disk-to-local virtual disk). Alternately,
Remote Replication (Legacy) only requires a single repository virtual disk.
• Data protocol supported — Standard Remote Replication is supported on both iSCSI and Fibre
Channel storage arrays. Remote Replication (Legacy) is supported only on Fibre Channel storage
arrays.
NOTE: Both remote and local storage arrays must be of the same data protocol -- replication
between Fibre Channel and iSCSI storage arrays is not supported.
• Distance limitations — Distance between local and remote storage arrays is unlimited using the
Standard Remote Replication premium feature. Remote Replication (Legacy) has a limitation of
approximately 10 km (6.2 miles) between local and remote storage arrays, based on general latency
and application performance requirements.
Examples Of Typical Use
Standard (asynchronous) Remote Replication is more network-efficient and generally more suitable in
environments that require fast, non-stop processing. Remote backup consolidation, long-distance
disaster recovery and 24 x 7 data protection are also common uses.
Synchronous Remote Replication (Legacy) is designed to provide replication between a relatively small
number of local systems that require business continuity — for example, data center-type operations,
local disaster recovery and other top-tier applications.
Upgrading To Asynchronous Remote Replication From Remote Replication
(Legacy)
When you upgrade a RAID controller firmware version that supports both legacy and non-legacy Remote
Replication premium features, all legacy Remote Replication configurations in the RAID controller remain
unaffected and continue to function normally.
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