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As CDP becomes a viable option for enterprise servers, organizations need to decide how extensive their deployment will be as it may require the use of one, two or even three CDP products to protect all desktops and servers. The makeup of the CDP host agent is a tip-off to the scope of data protection the CDP software can provide. File-system-based CDP host agents take advantage of existing TCP/IP networks and can recover data at the file-system or volume level, but may cause excessive server and network overhead in high-transaction environments.
CDP products with block-based agents minimize overhead by capturing changes at the volume level and transmitting all changes over IP or FC SANs. Block-based CDP agents can scale to meet the performance requirements of most mission-critical applications, but can introduce significant cost and complexity.
Selecting the right CDP product architecture for enterprise servers often comes down to whether the server is connected to a network or an FC SAN. If connected to an FC SAN, you need to determine if there are sufficient changes to app data to justify the deployment of an FC SAN-attached CDP appliance.
CDP products for network-attached servers come in many different architectures. CA XOsoft, for example, installs at the file-system level and is configurable as a standalone product and as a replication target on a secondary server.
VMware users may want to consider FalconStor's CDP Virtual Appliance for VMware. Although both CA XOsoft and FalconStor Software support VMware and the installation of host CDP agents on guest OSes, FalconStor installs its host CDP agent at the block level. The agent then stores the changed data to a volume presented over the corporate IP network by the FalconStor CDP Appliance. Once the CDP software creates a copy of the data on that virtual volume, the administrator may break off that virtual CDP LUN from the source and present it to any other operating system on that ESX server for recoveries or testing and development (see "CDP and VMware," below).
This was first published in September 2008