CDP moves into the maturity phase

CDP vs snapshot, at a glance

which applications benefit most from CDP


representative CDP vendors


"true-CDP" and "near-CDP." In true-CDP, every write is captured and transferred to the protection disk, and you can roll back to any point in time. (Note that recovering to an arbitrary point in time can lead to application inc integrity issues.) In "near-CDP" granularity is not at the file write level, and recovery can occur to specific points in time. Backup Exec falls into this CDP category, with snapshots taken at intervals. True-CDP products can often be c as near-CDP to save disk space and reduce network traffic.


Near, true, or snapshot?

At the start of the CDP debate, vendors used to fall clearly into one camp or the other: those offering “true” CDP, which most closely matched the definition of CDP as originally outlined by the Storage Networking Industry Association (SNIA), and those offering what many analysts referred to at the time as “near-CDP”—often solutions that offered log-tracking or highly granular time-based snapshot functionality but which might not always be able to roll back to any point in time. Over time, such distinctions have become less of a religious war, according to Rick Walsworth, director of product marketing at EMC, which recently announced Release 3.0 of its RecoverPoint appliance that incorporates much of the CDP technology from EMC’s acquisition of Kashya. “At the end of the day, it’s about levels of granularity. How granular do you need to be with your recovery, and how efficient is the system at achieving it?” says Walsworth.

While some analysts, vendors, and end users might beg to differ, Taneja Group analyst Eric Burgener says the debate between true and near CDP now amounts to, basically, yesterday’s news. “The distinction between true and near CDP has become irrelevant in the last few years,” says Burgener, adding that most end users seem more interested now in gaining transaction-consistency rather than in capturing absolutely any and every point in time.

That may be true, but there was more than one CDP user we came across who wouldn’t think of parting with its APIT functionality. Contrasting the merits of using CDP technology versus less granular point-in-time snapshots, CIO Matt Reynolds is quick to claim that taking disk-based snapshots is simply not good enough for the needs of the three most critical applications at his San Francisco law firm, Howard Rice Nemerovski Canady Falk & Rabkin. Reynolds uses InMage’s DR-Scout to protect what he identified as the firm’s three “level-one” systems, which need to be accessible within 15 minutes of any disaster: the company’s Exchange e-mail system, the lawyers’ work product systems for research and drafting documents, and the firm’s Adorant CMS time and billing system. Wanting real-time replication combined with the ability to roll back to any point, Reynolds also noted the need for a solution that would require minimal manual effort to either fail over or fail back in the wake of disaster.

“For our needs, snapshots are not good enough,” says Reynolds. “It could be as simple as a document in our system, the final deal on an SEC trade, or an e-mail that had to be sent before midnight. These are critical to capture and restore.” With snapshots, depending on the time of disaster and when the last snapshot was taken, these items might slip through the cracks.

Enterprise Management Associates’senior analyst Mike Karp offers some insight to help users differentiate CDP technology from their snapshot counterparts (see “What CDP isn’t,” above). Among the distinctions was his view that CDP is more of an event-based approach whereas snapshots are more time- (or schedule-) based. Enterprise Management Associates also offers a free IT Solutions Center on CDP with analyst input related to many of the CDP offerings on the market.