Dell PowerVault MD3260i CLI Guide - Page 67

6 Using The Remote Replication Premium Feature The Remote Replication 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 is designed for extended storage environments in which the storage arrays that are used for Remote Replication 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 is storage based, it does not require any server overhead or application overhead. You can use Remote Replication for these functions: • Disaster recovery - Remote Replication 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 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 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 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. 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. 67