Does Deduplication Make Storage Capacity Planning Difficult?

With all the technologies out now, and it not just deduplication, to optimize the use of primary storage capacity, the guidelines for how you estimate how much capacity you need in a given year needs to change. In some ways storage capacity planning is more difficult than it has been in the past. It has to change to keep up with the new capabilities of storage systems like thin provisioning, compression and deduplication.Storage capacity planning of a few years ago seems like a relatively simple task compared with the capacity planning of today. You estimated the amount of capacity that you were going to need based on organic growth and new application needs, then doubled that number and ordered the storage. In many cases no one batted an eye to the process. If you apply that same logic today you may end of with 50% or more of your capacity purchase never being used. In fact several vendors are claiming, and even guaranteeing, that you will need less storage if you replace your current storage solution with theirs.

You could continue to use the old math when calculating storage capacity needs and enjoy all the extra free capacity. It is important to remember though that storage is not wine, it does not get more expensive with age, unused capacity is wasted budget dollars as well as power and cooling. The time has come to factor all these techniques into your next capacity or even storage system upgrade. Of these capabilities deduplication, compression and thin provisioning probably will have the most impact.

Primary storage deduplication has been discounted by some in the industry. There are concerns about performance impact and data integrity; both those concerns are technology issues and either are or will be overcome. Some solutions are now claiming micro seconds of latency and not altering the data format. The other and more legitimate concern is how much duplicate data do you really have on primary storage. In the past I would say this is a valid concern, until server and desktop virtualization. Now there can be TB's and TB's of redundant data on the system. Deduplication can address that problem and result in massive savings. Estimating how much deduplication should factor into your capacity planning is difficult. If the environment is going to be heavy on the virtualization side, I would suggest at least a 3:1 reduction in the amount of storage you were going to purchase maybe more.

Compression is another optimization technique to consider. Compression gains optimization across almost all files, it does not require duplicate data. The data does need to be compressible of course but in almost every case the net is at least a 2:1 gain. In most cases compression is not an inhibitor to deduplication, most of the solutions work together, some are even integrated.

Thin provisioning helps in an area that deduplication and compression do not, capacity that is allocated but not in use. Essentially storage that is captive to a particular server. You can't compress or deduplicate something that is not there. The only way to optimize this capacity is to free it from being bound to a particular server. As we discuss in our Thin Provisioning White Paper, the technology is no longer limited to optimizing new application deployment but also to ongoing application use. Modern thin provisioning technology can reclaim deleted space from volumes as well.

In our next entry we will discuss how to roll all this information together to plan your next capacity upgrade or to plan a new storage system purchase.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.