By Dave Simpson
At least one vendor would like you to buy fewer disks. Hoping to solve the common "allocated-but-unused capacity" problem, 3PAR has introduced Thin Provisioning in the latest release of its InForm operating software. Although the software works only with 3PAR's disk arrays, it allows users to buy capacity only when needed.
"Thin Provisioning is the way storage is supposed to be," says Jarrett Goetz, senior manager, IT infrastructure, at Infinity Pharmaceuticals, in Cambridge, MA. Goetz says that, like most storage administrators, he used to over-budget and over-purchase disk capacity. In contrast, "with thin provisioning, I don't have to buy the disks until I need them," says Goetz. In addition to saving capital costs, he says that "another benefit is that the price of disk drives is going down rapidly and the technology—capacity and performance—is increasing."
How significant are the possible savings with 3PAR's ap- proach? Goetz says that he saved about $500,000 on the initial purchase of 3PAR's disk arrays and software, and that savings could be $1 million to $3 million as the company scales capacity. Infinity has only 3PAR storage systems on a storage area network (SAN) with about 30 Windows and Linux servers attached.
Studies have shown that at many end-user sites, actual used capacity can be as low as 25% of allocated capacity. Although all major disk array vendors have "pay-as-you-grow" capacity purchasing programs, 3PAR differentiates its "dedicate-on-write" technology from other vendors' "dedicate-on-allocation" approaches. With the latter approach, users have to purchase all the storage they will need up front. With dedicate-on-write (Thin Provisioning) technology, users can allocate as much logical capacity as needed while purchasing physical disks only when needed by applications. Capacity is drawn from a common pool only when applications actually write data to the storage array.
"When the system needs more capacity it automatically grows itself and pulls from a 'common provisioning group,' " Goetz says. "When that starts to run out of physical capacity we automatically get notified by 3PAR and they send more disk magazines."