Storage Methods That Prepare You for the Worst (Continued)

Virtualization, Mirroring, and Replication
Three of the more common backup methods used in today's IT world include storage virtualization, mirroring, and replication.

Storage Virtualization refers to the process of dividing or aggregating available storage devices and their capacities into "virtual volumes" without consideration of the actual physical storage-volume layout or topology, which can include various storage elements such as disk drives and redundant array of independent disks (RAID) subsystems. Storage virtualization typically requires storage area network (SAN) management software for centralization, which can assist you in allocating volumes and reassigning storage resources. There are several techniques for carrying out storage virtualization; two of the more common techniques are data mirroring and replication.

Mirroring (or Data Mirroring) is the process of copying production or other business-critical data on disk storage devices from one location to another as a "mirror image" of the information at the production site. Essentially, data mirroring creates a secondary or duplicate copy online, replacing the primary data in the event of an emergency. A mirrored copy eliminates the need for a daily, manual backup.

Replication (or Remote Replication), on the other hand, simultaneously duplicates data to a secondary system to ensure continuous access in the event that the primary system fails. The differentiating factor in remote replication is the use of a secondary system, rather than a virtual online "mirrored" copy.

Both data mirroring and remote replication eliminate the long wait time associated with loading and restoring data on backup tapes following a disaster. Both techniques also can replicate damaged or corrupted data as it enters the system, copying damaged databases in the process.

Storage virtualization, or the "blueprint" used to carry out data mirroring and replication, is essential in assessing and determining the parameters of your disaster recovery or business continuity plan. But how do these three processes figure into the implementation of an effective disaster recovery strategy?

Perhaps you should look at it more simply: storage virtualization is similar to the process that a general uses in mapping out his platoons before battle into their various groupings or "clusters," and when he gives the command to go into battle, his plan is "virtualized" into action. Though more crude than SAN management software, the general serves as the centralized control for his troops. Unfortunately, you cannot actually replicate the soldiers once they're gone, but data can be replaced and restored to the appropriate systems based on the storage virtualization process.

Both mirroring and remote replication simply copy data; key processes used the actual backup. But without the initial virtualization or "mapping" of the physical storage terrain, however, a successful mirroring and/or replication cannot take place.

Introduction

Tactics for DR Plan Implementation