Feature

CDP: Look before you leap

Ezine

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Raising the CDP bar
The "what point in time to recover" problem is being addressed by at least five CDP vendors--Asempra Technologies, Asigra Inc., Atempo Inc. (through its acquisition of Storactive Inc.), Mendocino Software and XOsoft Inc. (recently acquired by CA)--that offer a feature known as enhanced recovery management. Mendocino (including its OEM vendors EMC Corp. and Hewlett-Packard [HP] Co.) inserts event markers into the collection process, which are then monitored by a policy engine. By incorporating CDP-awareness of business processes and events, it's more likely data will be correctly restored on the first attempt.

CA XOsoft's CDP takes a different approach. It continuously captures application- or database-specific writes and update events. For recovery purposes, CA XOsoft creates a journal entry for each write and event. When corruption occurs, damaged data is rewound to the last consistent state. Because only changes since the latest consistent state are rolled back from the journal, recovery is fast. Atempo's CDP is aimed at the Windows environment (Microsoft Exchange and file systems) with technology that works similar to CA XOsoft's.

Asempra's CDP is transaction-aware and application-specific. Its technology communicates directly with Exchange, SQL Server and Windows file systems (including CIFS). Before a transaction is copied, it checks the integrity of all of the data prior to forwarding it to the recovery server. This

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allows Asempra to detect data corruption as it occurs and provide a marker to determine the best recovery point.

Asigra has a completely different CDP methodology. It's a two-stage continuous backup that agentlessly backs up any changes on Windows servers to the local collector (DS-Client) as they occur. The local collector aggregates the changes, compresses and encrypts them, and then sends them to the central collector (DS-System). The central collector automatically checks and verifies the data for consistency and recoverability. If it determines a file can't be recovered, it automatically asks for it again from the local collector. This provides a known consistency point for all recoveries, again providing a quick recovery time.

Asempra, Asigra, Atempo and CA XOsoft also allow an app (such as Exchange) to be recovered first, and to be up, running and writing transactions even if all the data, mailboxes and transactions haven't been recovered. As the data is recovered, the CDP system continues to protect the live app that's running.

This was first published in September 2006

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