Reliant - DR and Backup

Backup and Data Recovery Converge

Over the last few years the functionality provided by backup and disaster recovery systems have converged so that they now appear to be the same – at least on the surface.

Historically, backups have been based on making data copies while disaster recovery comes into play after a disaster happens. Backups and other fault-tolerant mechanisms are put to work to bring things back to operational condition.

While, historically, backups were stored on removable media, they have now given way to a continuous process wherein data is copied to disk based storage arrays — a mode of backup called continuous data protection (CDP).

Today’s data protection systems solve many problems of the past

Continuous data protection systems can backup data a single time rather than repeatedly. A single copy retains changes as they’re updated. In these systems, data can be rolled back to a point before which hardware failure or data corruption occurred.

Using a strategy in which single recovery data is available, it’s a good idea to make certain that the backup storage array and the backup server don’t become a single point of failure. To prevent this, data replication to an alternative storage device is prudent. Replication could also be to cloud storage or a tape library.

Continuous data protection has become a popular data backup strategy, as it deals with problems of data growth and increasingly limited backup windows. Continuous data protection is not scheduled by definition.

Snapshot, virtualization and replication play a major role in convergence

These three technologies are key players in the convergence of backup and disaster recovery technology. The reason is simply that recovering from a disaster can be accomplished without traditional data restoration. Instant recovery can occur while storage cost is minimized.

A differencing disk is a virtual hard disk, VHD, which is reserved to record changes in case they need to be backed out. A snapshot process redirects write operations to a differencing disk. These two concepts are essential to understanding instant recovery.

Instant recovery makes full-blown restoration unnecessary whenever there’s a copy of the data available online. The failed system can utilize data available on the backup storage array.

How do differencing disks and snapshots come into play? A snapshot is created before a failed server is allowed to use the data residing on the backup array. The snapshot results in the creation of a differencing disk. The failed server can use the data from the backup array for read operations. Writing takes place on the differencing disk.