Why and when to implement CDP

Time spent working and capturing revenue is much better than time spent recovering data. Mark Staimer discusses how SMBs can leverage continuous data protection (CDP) to gain a competitive advantage.

If you have critical applications such as email, databases, point-of-sale systems or financial transaction systems

where data can never be lost and it must always be up and running, you may want to consider implementing continuous data protection (CDP). CDP provides a recovery point objective (RPO) of zero and recovery time objective (RTO) of essentially instant recovery. Defined another way, CDP is a time-stamped backup stored on secondary disk. The appeal of CDP is its ability to quickly rewind applications to any point in time to find a consistent image of the data. CDP provides data protection against hardware failures, human error, malware, software failures and accidental deletions.

Don't confuse CDP server, virtual server or storage system based mirroring and snapshots. Mirroring provides data protection only from hardware failures. Any other type of data corruption or deletion will automatically be mirrored causing a rolling disaster. Snapshot products capture changes as points in time, with every snapshot checked for consistency before the next one is taken. However, most snapshots are not application aware and have difficulty in providing database or email consistent copies. Also, there are time gaps between snapshots. CDP captures changes continuously and consistently, without any gaps or missing data.

CDP ensures there aren't any gaps because it captures every file, block or table change as it occurs. And while data can be restored to any point in time with CDP, it can sometimes be a bit dicey determining which point in time to rewind to. This can make restores a trial-and-error process. If the recovery point is a point-in-time (PIT) after the corruption, the data must be recovered again from an earlier point in time increasing the recovery time. If the administrator plays it safe and chooses a recovery point too far back before the known corruption, the CDP recovery time can be worse than current methods. However, this is typically isn't a significant issue.

So if you are a small-midsized business, why do you need CDP? It's all about time. Time spent working and capturing revenue is much better than time spent recovering data. A great example is Microsoft Exchange, which is usually a key critical application for most organizations. Make no mistake, it is not a matter of if Exchange will have to be restored, it is a matter of when and how often.

Microsoft Exchange is extraordinarily difficult to restore with most data-protection applications. Restoring Exchange is complex and frustrating, including Exchange 2007. Even though it is relatively easier (much easier) than previous versions of Exchange, it is still quite complex and frustrating to provide complete restores. Ultimately, depending on the number of mailboxes and messages needing restoration, it can be extraordinarily time-consuming. These are typical steps to restore Exchange:

  • Apply last full backup

  • Apply transaction logs (if available)

  • Restore messages and transactions to each individual mailbox; this is time-consuming and often skipped, leaving a lot of data that's never restored

  • During the restoration process, Exchange is down and a temporary server is required
  • CDP is ideal for restoring Exchange; recoveries are painless and very fast. It first rewinds Exchange back to the last known consistency point and gets it running in seconds or minutes. After Exchange is back up, the CDP application allows point-and-click restoration of messages and transactions back to individual mailboxes in minutes.

    Ultimately the choice is yours. CDP is a very high level of data insurance. And just like insurance, only you can determine if the return is worth the investment.

    About this author: Marc Staimer is President and CDS of Dragon Slayer Consulting in Beaverton, OR. He's widely known as one of the leading storage market analysts in the network storage and storage management industries.

    This was first published in May 2008

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