Thin provisioning's fat chance during the credit crunch

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Written By: Peter Williams
Published: 3rd December, 2008
Content Copyright © 2008 Bloor. All Rights Reserved.

For me, thin provisioning of storage is a logical extension to virtualising it. Early on, vendors who offered thin provisioning solutions had to struggle against scepticism backed by FUD from some of the big hardware vendors not over-enthusiastic about a technology which helped customers buy less tin.

The inevitable happened. Gradually there was greater adoption of hardware-software solutions offering thin provisioning until, this year, most of the leaders now offer some thin provisioning flavour. IBM even offers it in its SAN Volume Controller (SVC) appliance—which effectively makes it available across multiple vendors' back-end hardware if used through an SVC.

Thin provisioning means allocating disk storage space only as it is actually needed—which avoids purchasing extra capacity only for it to sit idle (but spinning and using energy). Typically, only 25% of the total physical disk allocation for a standard system is actually needed. This makes thin provisioning a very green technology, reducing expansion of disk resources (footprint), energy and heat output—and therefore cost. Equally, since the provisioning can be largely automatic, it can greatly reduce the need for management of disk resources and capacity planning.

So are these tough economic times the point at which thin provisioning is really going to take off? Sadly, I suspect not, at least in a big way. While the cost savings that may be made once installed sit fairly well with the economic downturn, the capital investment and a trade-off in performance may muddy the ROI case.

The performance issue falls into a couple of categories. The first is that if you increase individual disk utilisation because the data is spread across less platters you also increase disk contention and so lower overall throughput performance. This may not matter for most applications but does for the mission-critical ones, particularly if there are SLAs associated with them.

Pillar Data Systems' thin provisioning system counters this problem with a quality of service (QoS) feature so that critical applications can be given message queuing priority over others; this can be fine tuned. It is, of course, an extra job for the storage manager to consider.

A second issue is the type of application and storage being dealt with. Database management systems tend to grab their whole allocated space straight away; even if there is a work-around it could complicate things—or it may be a case of applying thin provisioning only to part of the storage—which increases the management load in deciding what can and cannot be included and perhaps copying a few files around as well. Yet a major selling point of thin provisioning is that it can automatically deal with space allocation issues so that the storage manager does not have to.

Another possible factor is how well the software can utilise freed-up disk space following deletion of old data. Total thin provisioning space savings are increased if the software can handle this automatically, but some systems cannot. But, for instance, Compellent's Dynamic Capacity thin provisioning feature eliminates allocated but unused capacity as it goes while 3PAR's InServe architecture inherently reallocates unused blocks. (Having said this, companies may not all delete enough data to make this very fruitful.)

In addition, if yours is an enterprise with mixed vendor equipment, you may think long and hard before installing yet another vendor's purpose-built thin provisioning hardware/software solution, knowing that you will have to redirect all the files and databases to be included to the new system. It might mean a fair amount of planning so that realising a real return could take a while. Incumbents which can add thin provisioning to existing hardware may do better.

Every vendor's thin provisioning offering is different and most only work on their own specific hardware. For the reasons given, it may also be difficult to clearly demonstrate a fast ROI so vendors will need to work closely with their potential clients in achieving that.

Thin provisioning has a chance of benefiting from the credit crunch—some think it will be a fat one.

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