A big challenge is making things "green" or "greener." I think we all will admit that we didn't suddenly become environmentally conscious. For most of us, the need for greener storage has come from the fact that we have simply run out of power! One of the most challenging areas of storage to green is primary storage. Much has been written about making storage more green and much of that conversation has focused on data deduplication and MAID. For data that is at rest, those technologies are both valid and can deliver significant cost reductions in power consumption.
How can you make storage that has to spin, primary storage, more power efficient?
The active part of primary storage is always being accessed and is never at rest, so it would not get a chance to spin down and turn off with MAID. Since active primary storage is constantly being accessed, it is difficult to deduplicate it with a data deduplication system, as it may hinder performance. For the same performance reason, use of high-capacity SATA drives cannot be considered.
What can be done?
First, array systems in general will likely become more power efficient because the component makers (drives, controller chips, etc.) are under pressure to make their individual components more power efficient. This will be available more broadly and only make a marginal difference. The big advancement that is available today comes from virtualized storage platforms such as those made by 3PAR and Compellent. Each of these products offers a capability called thin provisioning. It is a capability that is often thought of as a way to save storage acquisition costs, but it also can decrease power requirements.
Thin provisioning allows you to allocate large partitions to application servers attached to the SAN but only physically use the actual capacity as data is written. This means you could allocate 500 GB to your Exchange environment but only physically be using 80 GB of actual disk space. Where the power efficiency of this kicks in is as you lay out the entire storage environment, you might, in total, allocate 15 TBs but only physically buy 5 TBs. Compared with a standard array where you would actually have to buy the entire 15 TBs, this is a net savings of 10 TBs. This ability to over-provision storage not only saves obvious upfront costs, but also saves the costs associated with powering and cooling that capacity.
The major risk to thin provisioning of storage is that you might actually run out of disk space! I've never met a client that has actually done this. Mostly, the storage solutions that have this capability also offer reports and alerts that will give plenty of advance warning when you are getting ready to run out of disk space. Pay attention to those reports! Understand how long it will take to order and deploy the new storage. If power is your primary concern, order an extra shelf of capacity, and have it racked and ready to go but not powered on. Most of the virtualized systems make adding additional capacity to the system automatic. Power it on and capacity is ready -- the virtual volumes will just grow into this new capacity automatically.
Thin provisioning is a viable method for controlling the power consumption costs of primary storage that also saves you money by not having to acquire the storage until you absolutely have to have it. Disk capacity isn't like a fine bottle of wine; it does not get more expensive with age. The longer you can delay a storage purchase, the more cost-effective that purchase will be.
George Crump is founder of Storage Switzerland, an analyst firm focused on the virtualization and storage marketplaces. It provides strategic consulting and analysis to storage users, suppliers, and integrators. An industry veteran of more than 25 years, Crump has held engineering and sales positions at various IT industry manufacturers and integrators. Prior to Storage Switzerland, he was CTO at one of the nation's largest integrators.