Symantec trumpets its Veritas File System (VxFS) as the only file system that properly handles storage that has been thin provisioned, a claim backed by thin provisioning system pioneer 3PAR. "Thin-friendly" means Storage Foundation does not reserve storage until it is needed to make sure thin volumes stay that way.
Symantec this week disclosed a Smart Move feature in Storage Foundation intended to automatically reclaim unused space during online migrations from fat (traditional) to thin storage. Symantec director of storage management Sean Derrington said SmartMove works with any storage array and supports Windows, Unix and Linux. "SmartMove only copies useful blocks when mirroring and does an online reclamation as you migrate from thick to thin," Derrington said.
3PAR was the first to work with Symantec's API, and 3PAR marketing vice president Craig Nunes said the reclamation capabilities will be in its next software release. All the major array vendors offering thin provisioning are involved in the program, although only 3PAR, Hitachi Data Systems and Hewlett-Packard have made their involvement public, Derrington said.
Taneja Group analyst Jeff Boles said poor communication between the file system and storage array can undo many of the capacity savings of thin provisioning. "This has been a long-term challenge for thin provisioning." Without visibility into the file system, you don't know what's going on. To really optimize storage, you need more intelligent connectivity between the block level and file level," Boles said.
Or as 3PAR's Nunes said, "Thin provisioning is a way to start thin. Reclamation is a way to stay thin."
"We've relied on the file system until now," Nunes said. "The file system tries its best, but now we do it under the covers, completely automated."
Boles wondered if other file system vendors will follow Symantec's lead.
"This sets up an interesting precedent," he said. "It will be interesting to see if people like Microsoft and Sun jump on the bandwagon and integrate their file systems with thin provisioning."