Continuous data protection
Once an acronym becomes popular, altering it -- even to better reflect the underlying technology -- is difficult business. CDP, the natural evolution of conventional backups, would probably benefit from a name change to something along the lines of "data recovery preparedness." After all, the objective of adopting a CDP solution is to ensure that your enterprise -- or selected business processes within -- can survive a disruption without data loss.
As many enterprises have been made painfully aware, the traditional backup paradigm has never provided an impenetrable data protection shield. In essence, conventional backup applications take a picture of selected databases or files at recurring intervals, typically each day at business closing time.
The approach, however, has severe limitations, most notably its long intervals between protective copies, which in the event of a disruption, translates to lost data. In today's world of highly interactive applications, a prolonged risk of data loss is fast becoming increasingly unacceptable, which is probably what triggered GlassHouse Technologies CTO James Damoulakis to title a recent BusinessWeek white paper "Best Practices: Are Backups a Waste of Time?"
Backups may not always be a waste of time, but the fact that just about every backup-software vendor has added CDP to its portfolio is probably the most unbiased acknowledgement of the importance of CDP -- and the limitations of traditional backup wares. CDP moves beyond backup's limitations by providing virtually infinite recovery points, an enormous improvement that leaves very little or no data at risk.
In the main, CDP solutions take one of two approaches: Either they use a host agent to intercept and replicate every write to disk, or they schedule frequent snapshots to create numerous volume images from which to restart in case of damage.
Less granular though easier to implement, the snapshot approach is worthwhile -- and perhaps less burdensome -- when full recoverability is not needed. For example, scheduling snapshots every 30 minutes can adequately protect an accounting system. In the event of a disruption, users can easily re-enter the last half hour of transactions after the proper files are restored from the latest volume image.
With more storage systems offering snapshot capabilities, this quasi- or near-CDP snapshot approach is certain to become more popular. Another notable advantage is that the snapshots can be the source of traditional backup operations so that tape copies for vaulting or data exchanges with other parties can be created offline.
However tempting near-CDP may be, it is no substitute for the no-bits-left-behind approach of a true, host-agent CDP solution. Recovery is not as easy with the host-agent approach because it requires applying data changes against a known good copy of the affected file or database. But true CDP makes it possible to bring data back at the very instant preceding the damage, which is quite a departure from the a priori, fingers-crossed decision one has to make when scheduling near-CDP and backups.