Which IT manager hasn't silently cringed at the Oliver Twist-like cry of "Please, sir, I want some more" from one or many business units knowing, at the same time, that there is a vast stash of unused storage capacity lurking in the company's 'cellars'?

Thin-provisioning applications are among the latest weapons in the battle of the bloated storage budget. Several vendors are now pushing these optional features of familiar storage systems as a way for IT execs to send a powerful message to storage-hungry business units: finish what's on your plate before coming back for more.

The back-and-forth between IT execs and users has become an all-too-familiar exchange. "It has almost become a ritual," notes Ernest Wurzbach, director of portal operations at Ask.com. "Those of us responsible for managing storage and storage budgets know how much allocated space winds up being attached to products or applications, but never gets used."

Waste not, want not

Unused capacity is a natural byproduct of traditional storage-allocation methods, says Tony Asaro, an analyst at Enterprise Strategy Group.

"Normally, if I want to provision a certain amount of capacity for a certain project, I must allocate that much capacity. Say it is 1TB. In reality, the user will probably only need about one-tenth of that space immediately, but I've had to allocate the whole terabyte," Asaro says. "So the other 900GB cannot be used. There is no access to it. Now, if I do this for every application, I will quickly have a storage system that is 100 percent allocated but not fully utilized."

That's exactly the situation Ask.com wanted to avoid. Rather than letting a lot of storage capacity earmarked for specific users or business units go untouched for long periods, the information-retrieval giant wanted to use every scrap of capacity available immediately upon the purchase of a single storage architecture for its Excite, iWon and My Way brands.

The company, formerly known as Ask Jeeves Inc, settled on 3PARdata's InServ Storage Server and added in the 3PAR Thin Provisioning feature, which allows Ask.com to capture snapshots of "capacity-less" online volumes that can be pressed into service. In addition, Ask.com makes use of another of 3PAR's so-called dedicate-on-write options, Virtual Copy, which also turns up empty volumes available for testing or off-host backups, according to company executives.

Wurzbach says he's been able to shave about 25 percent off overall storage expenses and has salvaged the 65 percent of allocated storage that is wasted when provisioned through traditional means. "We were able to reclaim all of the over-allocated storage, as well as educate project managers on how to realistically forecast their needs," he says.

Other storage vendors now rushing forth with thin-provisioning options include mainstay suppliers such as Hewlett-Packard, Network Appliance and Overland Storage. Joining them are LeftHand Networks Inc. and Compellent Technologies Inc.

All are trying to make the business case for thin provisioning. "The rationalization for these products is a savings on capital costs, because you don't have to buy as much capacity upfront," Asaro says. It's an argument that proves persuasive to IT leaders loath to continue buying storage capacity that is virtually useless, he says.

"Of the companies we polled recently, 58 percent said they were aware that they have stranded storage in their organization, and half of those had to buy new storage systems regardless," Asaro reports. He says there is a "simple elegance" to thin provisioning that forces users to be accountable for the amount of storage they consume and imposes best practices on executives assigning capacity.

The simplicity surrounding thin provisioning appealed to senior IT executives at Commerce Bank & Trust in the US. "We can underestimate the amount of storage space we need and then always grow it," says Steve Haas, the financial services company's IT security officer.

Thin provisioning also helped Commerce Bank with many of its struggles to meet the disparate storage needs of its departments and programs. "There is a huge difference in the specific sizes our various users require. For instance, we might have a power user out there who requires 500GB of space and another that needs about 20GB. Thin provisioning allows you leeway," Haas says.

Commerce Bank uses LeftHand Networks' thin-provisioning tools. The financial institution has three clustered Network Storage Module 200 storage devices that accommodate about 30 of its servers. By choosing LeftHand's thin-provisioning capabilities, the bank continually monitors the need to add capacity. "We really appreciate the notifications we get when we hit the soft thresholds that tell us we are running out of space. That happened this morning, as a matter of fact," Haas says.