Dell 32XX, 34XX, 38XX, 36XX manual Replication Repository Virtual Disks, Replication Relationships

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.

Replication Repository Virtual Disks

A replication repository virtual disk is a special virtual disk in the storage array that is created as a resource for the RAID controller module owner of the primary virtual disk in a remote replicated pair. The RAID controller module stores replication information on this virtual disk, including information about remote writes that are not yet complete. The RAID controller module can use this information to recover from RAID controller module resets and the accidental powering down of the storage arrays.

When you activate the Remote Replication (legacy) premium feature on the storage array, you create two replication repository virtual disks, one for each RAID controller module in the storage array. An individual replication repository virtual disk is not needed for each remote replication.

When you create the replication repository virtual disks, you specify the location of the virtual disks. You can either use existing free capacity, or you can create a disk group for the virtual disks from unconfigured capacity and then specify the RAID level.

Because of the critical nature of the data being stored, do not use RAID Level 0 as the RAID level of replication repository virtual disks. The required size of each virtual disk is 128 MB, or 256 MB total for both replication repository virtual disks of a dual-RAID controller module storage array. In previous versions of the Remote Replication (legacy) premium feature, the replication repository virtual disks required less disk storage space and needed to be upgraded to use the maximum amount of replication relationships.

Replication Relationships

Before you create a replication relationship, you must enable the Remote Replication (legacy) premium feature on both the primary storage array and the secondary storage array. You must also create a secondary virtual disk on the secondary site if one does not already exist. The secondary virtual disk must be a standard virtual disk of equal or greater capacity than the associated primary virtual disk.

When secondary virtual disks are available, you can establish a replication relationship in the MD storage management software by identifying the primary virtual disk and the storage array that contains the secondary virtual disk.

When you first create the replication relationship, a full synchronization automatically occurs, with data from the primary virtual disk copied in its entirety to the secondary virtual disk.

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