What does CDP have to do with ILM?

* Clearing some of the confusion caused by Three Letter Acronyms, or should we say, TLAs

In the high-tech world we are inundated with TLAs (Three Letter Acronyms). CDP (continuous data protection), ILM (information lifecycle management), SRM (storage resource management) - pick your favorite existing three-letter combination or make up your own, the alphabetic jumble is there to confound you.

Moreover, for those who can’t tell the players without a scorecard, things get even worse when they try to understand the relationship between one TLA and another.

When it comes to storage, the alphabet soup is as confusing as in any other area. So one of my correspondents should certainly be forgiven for asking the question, “what does CDP have to do with ILM?”- and then perhaps for adding under her breath - “and who cares, anyway?”

Managing information across the various phases of its lifecycle means much more than just moving data from hardware tier to hardware tier as the data's value changes. It also means applying various “tiers of service” to the data. Nowhere is the importance of the software providing that service clearer than when it comes to questions of data availability.

We can all agree that data availability is important, and certainly the need to ensure availability levels is one of the chief reasons we see increased usage of service-level agreements (SLA) these days.

Most SLAs are quantitative in the sense that “99.9% availability” means that services levels fall out of compliance if data is unavailable for more than 8 hours and 45 minutes over the course of a year. Typically high value data with a recovery time objective (RTO) as demanding as “three nines” (99.9%) would necessitate storing recent backups - at least the incrementals - on local (nearline) disk devices so that they can be retrieved quickly.

Many SLAs also assert qualitative requirements for availability. Such recovery point objectives (RPO) might demand that data must be recoverable to within an hour’s worth of granularity - in other words, no more than an hour’s worth of data may be lost after any downtime event. An RPO like this might be met with snapshot software set to capture changes every 60 minutes.

Unfortunately, hardware capable of providing the best RTOs offers no assurance whatsoever when it comes to RPOs. For some key applications - e-mail, perhaps a database, whatever a company defines as being “business critical” - the best RTOs without the finest RPOs are simply not good enough. These need instant (or near-instant) recovery at the data event level.

Event-based data recovery (that’s what CDP ultimately is) captures each change within a file or database at the byte level - only the changed bytes are written to the storage medium, which invariably is disk. Because CDP offers byte-level recoverability from disk, it provides RPOs and RTOs that traditional tape-based backups (full backups plus incrementals) are incapable of providing.

Whether or not you have applications that warrant the level of protection offered by CDP depends on the demands imposed by your SLAs. If file-level or message-level recoveries are needed for your e-mail service, the odds are you and your local CDP sales rep will be meeting soon. Ditto if all your companies revenue depends on a single database or application. Remember, however, that one size does not fit all when it comes to CDP, and an e-mail application may not be at all suitable for your Oracle team’s needs.

So ILM and CDP really do belong in the same bowl of alphabet soup. And that’s the truth. QED.

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Copyright © 2006 IDG Communications, Inc.

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