|
To address this problem, Knoerer evaluated FC SAN-based CDP appliances, selecting EMC's RecoverPoint CDP. After a proof of concept followed by a three-month trial, Knoerer implemented the CDP appliance in early 2007 and witnessed a big reduction in database recovery times. "RecoverPoint reduced our database recovery times to two to four hours, depending on database traffic," says Knoerer.
Although Siemens used EMC's PowerPath to split writes at the host level, EMC's RecoverPoint also takes advantage of new protocols in FC switches and FC director line cards that can split host writes at the fabric level. The EMC RecoverPoint CDP appliance logs on to either a Brocade AP-7420B Multiprotocol Router FC switch or a Cisco Systems Inc. MDS 9000 family FC director with a Storage Services Module line card. EMC RecoverPoint requests that the service begin copying writes for a specific host's data stream, which is then sent to the RecoverPoint appliance over the FC connection.
Symantec's CDP/R also offers an alternative to deploying a CDP host agent. If the host server is running Symantec's Veritas Storage Foundation, Veritas Volume Manager (part of Storage Foundation) can discover this LUN and then create a mirror between the primary volume on which the database resides and the virtual LUN presented by the CDP/R appliance. In that configuration, Veritas Volume Manager acts as the write splitter to support transaction-consistent databases, although users must install its CDP/R host client or wait until the mid-2008 release of the next version of Veritas Volume Manager, which will natively support this functionality.
Database consistency
FC SAN-attached CDP appliances maintain three levels of recoverable database images: crash consistent, transaction consistent and CDP consistency groups.
A crash-consistent image is the default-recoverable database image that all block-based CDP products provide. Should a database corruption occur, storage admins may recover the database to any past point-in-time. However, full database recoveries still depend on the database admin to replay the database transaction logs to complete the recovery to a state where the restored image is usable by the database.
|
