Dell PowerVault MD3820f - Manual (Page 207)

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Premium Feature—Remote Replication
The following types of Remote Replication are supported on the MD storage array:
• Remote Replication — Standard asynchronous replication using point-in-time images to batch the
resynchronization between the local and remote site. This type of replication is supported on both
Fibre Channel and iSCSI storage arrays (not between).
• Remote Replication (Legacy) — Synchronous (or full-write) replication that synchronizes local and
remote site data in real-time. This type of replication is supported on Fibre Channel storage arrays
only.
About Asynchronous Remote Replication
Standard Remote Replication (asynchronous) is a premium feature that provides RAID controller-based
data replication between a local and remote storage array on a per-virtual disk basis. By identifying
primary (local) and secondary (remote) virtual disk pairs, called replicated pairs, write operations to the
primary virtual disk of the pair are tracked by the RAID controller firmware and captured in a point-in-
time image and transferred to the secondary virtual disk in the pair.
Remote Replication groups allow you to manage synchronization of both virtual disks to create a
consistent data set across local and remote storage arrays. Point-in-time images on the primary virtual
disk and the secondary virtual disk can be resynchronized in a batch approach that increases replication
throughput. When data synchronization completes, the system uses the point-in-time images on the
secondary virtual disk to ensure that the data is maintained in a consistent state during subsequent
synchronization operations to the secondary virtual disk.
NOTE: The standard Remote Replication premium feature is supported on both iSCSI and Fibre
Channel storage arrays.
Remote Replicated Pairs And Replication Repositories
Replicated pairs, comprising of a primary and secondary virtual disk, contain identical data copies as a
result of data synchronization. Replication repository virtual disks are used to manage replication data
synchronization and are required for both the primary virtual disk and secondary virtual disk in a
replicated pair.
A replication repository consists of the following types of data:
• Resynchronization and recovery point images for both primary and secondary virtual disk.
• Log information that tracks regions on the primary virtual disk that is written between synchronization
intervals. These logs are only used on the primary virtual disk, but are also written to the secondary
virtual disk in case of a role reversal.
• Statistics for each replicated pair.
The replication repository is normally created automatically when you create a replicated pair. However,
you can also create the repository manually.
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