Let's measure CDP against those criteria:

• Initial reaction to CDP products is typically excitement about the possibility of eliminating backups and having near-zero recovery time objectives (RTOs) and recovery point objectives (RPOs) without spending a fortune.



• The number of vendors in the CDP arena is expanding. The Storage Networking Industry Association's "CDP Buyer's Guide" lists approximately nine vendors/products. If you also include snapshot-based, near-CDP products, the list grows.



• Adoption risk is the sticking point for CDP-type technologies. Initial positive reactions may be replaced by skepticism or questions about a product's maturity and reliability.

Enter the giants
There are signs CDP is gaining traction, as evidenced by the large vendors embracing the concept. Oracle has incorporated CDP-like functionality, called Flashback, into Oracle 10g (see "Oracle Flashback," at right) that enables fast rewind of databases to earlier points in time. IBM is testing the waters with IBM Tivoli CDP for Files, a product focused primarily on protecting desktops and laptops. Symantec/Veritas and EMC are also talking about introducing CDP products.

			Oracle Flashback
			Since the introduction of RMAN in Oracle 8.0, Oracle has steadily improved data protection functionality in its products. Introduced in Oracle 9i and significantly enhanced in Oracle 10g, Flashback provides a set of SQL commands that lets users view data as it existed at various points in time. This allows you to quickly identify points of corruption and to restore a database or table to a point immediately prior to the corruption. Designed to protect against logical corruption only, Flashback must be combined with other technologies, such as backup and replication, to protect against physical loss. While not a complete continuous data protection solution, it's a dramatic step toward a significantly reduced recovery point objective and recovery time objective.

But the most significant entry into this space has to be Microsoft with its System Center Data Protection Manager (DPM) 2006. CDP purists might cringe to see DPM grouped with other CDP products (see "Defining CDP," previous page). Technically, DPM might be considered a snapshot repository and management product. Using replication and the Windows Volume Shadow Copy Services (VSS) infrastructure, DPM provides automated data protection functionality to file servers with far better RPO/RTO capability than traditional backup. It also eliminates the nightly backup window.

Microsoft DPM works with Windows 2000 Server, Windows Server 2003 and Windows Storage Server 2003 to protect server volumes, folders or shares. A DPM agent initially creates and sends a replica of each protected object to a DPM server. The agent then logs byte-level changes and periodically (typically hourly) replicates those changes to the DPM server. The DPM server catalogs this information in its SQL Server database and uses VSS to create point-in-time copies of protected objects based on administrator-defined policies.

The default policy is to create shadow copies three times a day. Given the VSS limit of 64 shadow volumes for each protected object, this provides approximately 30 calendar days (20 business days) of disk-based DPM recoverability. The granularity can range from hourly to daily, and the oldest copy is removed when the 64-copy limit is reached. This limit dictates that an organization should establish an archiving policy to ensure maintenance of older data.

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