SANs take on mirroring

Providing redundant storage subsystems is one cost of data mirroring.

That's a pricey proposition if an organization deploys identical high-end storage devices in both the production and backup facilities. But storage-area networks may help defer that expense. SAN virtualization masks the differences among storage subsystems, creating a single pool of virtual storage in the SAN that is accessible to any server connected to it. This means an agency could mirror data between a top-of-the-line system and a cheaper disk array.

Virtualization "allows customers to potentially avoid having to buy more expensive storage arrays," said Tom Isakovich, president and chief executive officer of San Jose, Calif.-based TrueSAN Networks Inc.

But Wayne Lam, vice president of marketing at FalconStor Software, warns that mirroring via SAN can generate excessive storage traffic. A host writing to storage does this twice, once to each mirrored drive, thus generating double the storage traffic over the SAN. But specialized storage server appliances, such as FalconStor's Infrastructure Platform for Storage Networking, or IPStor, can take on the extra work to reduce traffic, he said.