News

posted on 24 April 2008 09:25

IBM's SAN Volume Controller (SVC) is to gain a thin provisioning capability.

The SVC is a storage virtualisation product that is linked to a Fibre Channel fabric switch or director and virtualises the multiple disk drive array storage behind the fabric for storage-accessing servers. Its in-fabric location contrasts with edge-of-fabric virtualisation such as HDS' USP-V and in-director virtualisers like EMC's InVista.

Thin provisioning is a technique whereby applications are allocated disk space (a LUN or logical unit number) of a given size but physical disk capacity is only allocated on an as-needed basis thus deferring disk capacity purchases until really needed and also increasing drive array utilisation.

An IBM blogger, Barry Whyte, says  that IBM will introduce Space Efficient Volumes/Vdisks (SEV) with the Vdisk term meaning, we think, virtual disks. SEV is IBM's way of describing/implementing thin provisioning.

He also says that SVC will be able to make thinly-provisioned flash copies, called Space-Efficient Flash Copy (SEFC). A target disk needs to be created as an SEV for this to happen.

IBM says it has now shipped in excess of 12,000 SVCs to 4,000 or so customers. EMC says it has 200 installations of InVista while HDS claims it is a storage virtualisation leader  but doesn't give out the number of USPs shipped with the virtualisation license needed. By any reasonable judgement in-director storage virtualisation has failed.

Common sense says IBM has sold and is selling more SAN storage virtualisation products than enyone else, including HDS, and is wildly outselling EMC whose InVista is a work in progress. (Odd that it shares two syllables with a certain Microsoft operating system also described as a work in progress.)

^{[Paul Roberts, news editor.]}