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What are continuous data protection software pros and cons?

Through disk-based backup, continuous data protection enables backups to take place more often. Discover how to repair the technology's cost and capacity problem.

Converged backups and archives are generally based around the use of continuous data protection. CDP was originally introduced as a mechanism to circumvent the problem of shrinking backup windows.

Prior to the introduction of continuous data protection software, most organizations performed a nightly tape backup. The problem, however, was that many organizations found themselves having to protect a constantly growing data set within a strict backup window. Although there are a number of techniques for expediting tape backups, there is a limit to the amount of data that can be backed up within a given period of time.

Continuous data protection software sought to solve this problem by transitioning from tape-based backup to disk-based backup. The technology works by creating an initial data copy and then using changed block tracking to back up the storage blocks that have been modified -- or newly created -- since the previous backup. This technique minimizes the amount of data that must be backed up within each cycle and effectively eliminates the backup window. As such, backups occur every few minutes, as opposed to once per night.

Fixing an issue created by CDP

While CDP solved a number of backup problems, storage cost and capacity became major issues because continuous data protection software used hard disks as its backup media. After all, each disk has a finite storage capacity, and disks cannot be swapped out as easily and inexpensively as tapes. Creating multiple data protection tiers solved this problem.

In general, continuous data protection software allows for a short-term tier and a long-term tier. The short-term tier stores the most current data and usually exists on a high-performance storage array whose disks can collectively deliver a sufficient level of IOPS for efficient data protection and recovery.

As recovery points age, the continuous data protection software moves them out of the short-term storage tier and on to the long-term storage tier. This tier may leverage commodity disks, but it is more common for it to be based around tape or cloud storage.

It is likely that this two-tiered approach to data protection directly led to the convergence of data backups and archives. Initially, this method of data protection was simply used to reduce storage costs, while also overcoming capacity limitations stemming from the use of disks. More recently it has evolved into backup and archival convergence. Today, such products may also include features such as automatic data expiration, e-discovery and the ability to create multiple protection groups, each with its own archival policies.

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