The Skinny on Thin Provisioning -

The Skinny on Thin Provisioning

Thin provisioning is something of a tightrope act, promising users loads of storage in the hopes that nobody will actually need it all, while delivering only what is absolutely necessary. Yet end users seem to like it nonetheless.

"We were buying more storage than we actually needed at any time because we had to over-allocate to make sure that the capacity was there when we needed it," said Ryan Engh, IS Infrastructure Manager at Wasatch Advisors, a financial firm operating out of Salt Lake City. "Now, with DataCore thin provisioning, we only allocate what we need when we need it, we've dramatically reduced our storage over-capacity, and we have effectively reduced our costs and energy footprint by more than 50 percent."

Analysts appear to like it, too.

"More mainstream vendors have announced thin provisioning offerings recently: Hitachi with the launch of their USP-V product, EMC with the DMX-4 advance announcement at EMC World, HP with their Dynamic Capacity Management announcement, although this is not truly thin provisioning," said ęłęóęłęóAndrew Reichman, an analyst at Forrester Research. "That combined with the acuity of the utilization problems in storage environments and the general interest in green technology has made this particularly hot."

Not surprisingly, vendors are rushing in to meet the demand.

"Thin provisioning is a way to help increase utilization of expensive IT storage assets," said Frank Kettenstock, vice president of marketing for MonoSphere, a provider of storage capacity management software for NetApp environments. "Secondly, it provides provisioning ease-of-use improvements so that storage administrators can now perform many tasks without taking storage off-line, can more easily move storage, or more easily increase or decrease storage size."

Space Reserved

Everybody, it seems, wants to reserve space for their own use. This includes the users, the admins, the operating systems, the applications, etc. Before you know it, there is a whole lot of space on a storage array that is reserved and not available to be used. Furthermore, every time someone wants more space it requires manual intervention — thin provisioning is a way to make this an automatic process.

"DataCore's thin storage can trim conventional fat storage from 10TB down to 4TB," said George Teixeira, CEO and president of DataCore Software Corp. "It makes storage use more efficient — reducing the number of disks and therefore lowering the cost of energy and cooling cost."

He said the benefits include better consolidation and efficient load balancing, reduced time and resources required to perform storage provisioning tasks, and smarter purchasing.

Reichman said thin provisioning allows physical storage to be reserved only when data is written, not when the application is first configured. In traditional storage provisioning, application teams guess at how much storage they might consume and that full amount is reserved on day one. The amount reserved can be used only by that application, and not by others. This means that large portions of costly storage go unused, and consume power and cooling resources in spite of the fact that no data is actually written to that disk.

"There is a soft reservation that allows the server to think that it has the full allocation amount, but does not commit physical disk until the consumption level actually rises," said Reichman. "This way, the environment purchases and deploys only the amount consumed, plus a buffer amount for growth."

There are, of course, numerous approaches to thin provisioning. Reichman said highly virtualized arrays such as those by 3PAR and Compellent allow blocks to be placed anywhere within the system, and growth to be seamless. HDS, on the other hand, added a "wide striping" capability to its arrays to enable thin provisioning.

"3PAR, LeftHand and Compellent have the most experience with the applications that use thin provisioning and the hurdles associated with deploying it," said Reichman. "The value of that should not be underestimated."

HDS, NetApp and 3PAR sell thin provisioning as an added feature of their hardware arrays. DataCore sells software that can run on just about anything. Pricing starts at around $1,000, and a free 30-day trial is available.

"What we do is more like VMware — we offer software that runs independent to the hardware," said Teixeira. "It works with any storage and can serve that storage to any Windows, MacOS, Linux, UNIX, Solaris, AIX and NetWare systems."

Thin Ice

But there are potential dangers. Kettenstock equates thin provisioning with airline over-booking. Not everyone who buys a ticket on a flight always shows up. So airlines sell more tickets on the flight than seats on the plane, anticipating that a handful of passengers will not make the flight. Thin provisioning is similar. Most application owners ask for more storage than they really need, so storage administrators can thinly provision it so it looks to the application owner like they have more storage than they really have. But therein lies its danger.

"If all the passengers show up to an overbooked flight, angry passengers get bumped off," said Kettenstock "If some of the applications use all their allocated storage, the shared storage pool for many storage consumers becomes full and none can save any more data."

Thin provisioning, then, makes it appear to each storage consumer that there are significantly more storage resources available than are actually present. The risk is that one or more storage consumers can fill all the actual storage, resulting in disastrous situations where multiple applications and end users are unable to save data.

MonoSphere attempts to solve this for NetApp environments with its Storage Horizon software. It provides early warning to storage administrators when space will run out, allowing them to resolve the issue before it becomes an emergency. It also provides an enterprise view so storage admins can quickly see everything they have, how much is used, how fast usage is growing, and be alerted to any problem areas.

"Thin provisioning is still in its early stages and being implemented by the early adopters in areas of low impact," said Kettenstock. "It needs to mature to be widely deployed by the early and late majority."

Reichman believes such tools have a part to play in the growing acceptance of thin provisioning.

"Monosphere offers capacity reporting software that allows administrators to see how much storage is actually consumed," he said. "Since thin provisioning means that there is a mismatch between what the server sees and what is happening on the storage side, the new version of Monosphere Storage Horizon reconciles this disparity and allows administrators to get an accurate and detailed view of thinly provisioned storage."

Regardless of risk, however, the bottom line on thin provisioning's popularity is cost. Using less storage for more users is bound to get anyone excited.

"Thin provisioning can be a great solution for budget-strapped IT managers," said Mike Karp, senior analyst at Enterprise Management Associates. "It saves money, time, worry, and is 'green,' so it makes companies good environmental citizens."

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