Point-in-Time Copy : Yesterday, Today, and Tomorrow
Alain Azagury · 2002
This paper describes the functionality of a point-in-time copy facility and describes both the benefits and drawbacks of providing this facility on the storage subsystem. While there are other benefits, the biggest benefit of providing this facility on the storage subsystem is performance; we do not needlessly add load to the storage network or host as part of making the copy. The biggest drawback is that the storage subsystem in today's world is only aware of data at the level of logical units and blocks; this makes it hard to meaningfully perform copies at a granularity of less than an entire logical unit