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Storage Pipeline: Backup Strategies, Solutions and Architecture: Page 8 of 13

The hottest buzzword in point-in-time data protection today is CDP, or continuous data protection. CDP is a blend of backup and snapshot technologies designed to offer even greater granularity than conventional snapshots. More important, it maintains a historical record of all changes made to stored data and supports restoration to any point in time. This is where CDP differs the most from conventional snapshot technology--while snapshots are scheduled to protect data at specific points in time, a CDP system should be capable of monitoring all storage transactions and offering unlimited, arbitrary recovery points. A tall order, but CDP products fitting these criteria are available in both software and appliance form, and can be based on block-, file- or application-level strategies (see "Data Do-Over").

Block-level CDP is designed to protect an entire volume or LUN by monitoring block-level changes to data on the fly. On the plus side, the whole volume is protected, so all applications using that volume receive the same protection. On the other hand, block-level CDP is non-selective, so all data on that volume receives CDP regardless of its importance; a block-based system doesn't differentiate between data types or offer granularity beyond volume-level.

The next option, file-level CDP, protects individual files, which account for well over 90 percent of the data in use today. By offering file-level granularity, this type of CDP can protect most applications while giving an administrator the flexibility of including or excluding specific data groups from protection. For the ultimate in integrated protection, application-level CDP will let you protect down to individual database transactions--even e-mail messages, in the case of Exchange-based CDP. Application-level CDP may be a part of the application or a third-party offering based on published APIs.

Like most emerging technologies, CDP is still trying to find its place in the data protection spectrum. Some vendors are pitching it as the Holy Grail, while others are calling it a replacement for conventional backups in the small-business space, under the assumption that there's no need for tape anymore if your data is "continuously protected." As usual, the truth lies somewhere in the middle.

Without a doubt, a number of businesses--financial firms and large online retailers, for starters--would be foolish not to have continuous protection in place. For the rest of us, it comes down to the simple question of bang for the buck.