Summary

This chapter examined the technology and methods of remote copy storage management applications. Remote copy is used to create data redundancy for disaster recovery purposes. With remote copy, writes are forwarded from a primary storage controller to a secondary and/or tertiary storage controller. Controllers in a remote copy system can be located locally within the same building or campus as well as remotely, hundreds of miles apart.

The requirements for remote copy systems can be extremely challenging. The performance of the remote copy system must be fast enough to not hinder a system's application performance, and write ordering of transmitted data must be guaranteed to ensure data consistency.

One of the constraints is the speed at which signals propagate in fiber-optic cabling, which means that distance is also a limiting factor. The technique of using nearby bunker storage for high-speed transmissions and then forwarding data from the bunker site to a distant tertiary site has been adopted successfully by many large companies.

Despite the technology challenges, the capabilities of remote copy have been proven many times by companies that relied on them to maintain operations following a disaster. The use of remote copy technology is expected to grow as more companies bolster their disaster recovery capabilities.