Storage Tip: Increase energy efficiency of stored data

April 9, 2007 —

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What seems to be the problem? IT organizations are concerned about real heat as the hardware components of the IT infrastructure heat up as they function. To keep a normal temperature, the infrastructure, including storage, must be cooled. The double whammy then is that power must be used for both heating and then cooling. Since electricity is already relatively expensive, IT organizations have an incentive to try and control their energy costs. Moreover, in many cases, IT is finding that data centers may be running up against limits (sometimes imposed by third parties) on power use, and expansion may be out of the question. Storage administrators must give attention to how the storage infrastructure can be made more cost efficient.

What do you need to know? One approach is to get more out of the storage that you already have by increasing the utilization factor over time. One way to accomplish this is to consolidate underutilized disks into fewer, but on-average fuller, disks. You can then either idle some disks that are not used and take an immediate power savings or you can wait and fill them up over time with new data without increasing power consumption.

How do you do this? The data must be on a storage area network (SAN) that serves multiple servers. You have a choice of either virtualization or brute force. Configuration management is a lot easier with virtualization, and you don't have to guess how much storage each server will actually use. The brute force alternative is the painful manual reconfiguration of the SAN. The choice is yours. The first approach was better utilization.

Two other strategies for energy efficiency are: 1) reduce the amount of data on spinning disks and 2) move as much data as possible to more energy efficient storage (which is a benefit of using tiered storage). Both strategies require strong data retention management policies for storage.

Reducing the amount of data on spinning disks comes about from the planned destruction of data that no longer serves a business purpose. Having a formal policy in place would be a good idea in order to meet any legal requirements, such as conformity to the changes in the Federal Rules of Civil Procedure for civil litigation. Now destroying data by itself does not save energy if disks continue to spin, but it defers the need to add additional power-consuming disks. You may be able to also consolidate (using the first approach) and idle some disks until storage demand picks up again.

Then there is the energy efficiency generated by tiered storage. Any non-primary tier of storage is likely to be more watts-per-gigabyte-friendly than primary storage, so moving data, say for active or deep archiving purposes, to a non-primary tier may lead to greater energy efficiency. Take for example massive array of idle disks (MAID). In a MAID array, most of the disks are idled down since the assumption is that only infrequently accessed data is put on a MAID array. And an idle disk is very energy-friendly as it does not use any power. However, tape can also be very energy-friendly. A tape cartridge that is not being accessed in a tape drive does not consume energy.

What can you do about it? Storage is not the primary culprit as far as energy usage in the IT infrastructure is concerned, but the seemingly inexorable growth in storage continues to be a significant factor in the growth of power and cooling demands. Therefore, managing your storage with an eye towards energy efficiency is important. Doing better space management so that you can use a higher percentage of your existing disk is one way that you can make a difference. Pruning excessive and unnecessary storage that clogs up disks is another approach to deferring the need to add power. Moving less frequently-accessed data to more watts-per-gigabyte efficient storage is another strategy that you can use. So you have a number of choices on how to improve storage-energy efficiency. Yes, they involve some work, but the results show up in the greening of the storage budget.

storage.itworld.com