Dell PowerVault MD 32XX/36XX Series Storage Arrays CLI Guide

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.

In the event of a disaster or a catastrophic failure at the primary site, you can perform a role reversal to promote the secondary virtual disk to a primary role. Hosts then are able to read from and write to the newly promoted virtual disk, and business operations can continue.