Thin provisioning or to some “just-in-time” or dynamic provisioning of storage volumes – pick your favorite buzz word –is all the rage amongst RAID array vendors. In the good old days - last year in this business – when creating storage volumes for one of their charges, administrators assigned the total requested capacity for the volume up front. While this seemed simple enough, it required clairvoyant administrators to gaze into their crystal balls and foretell how much capacity will be needed - at least in the near future - no small feat in a large dynamic storage realm. Luckily, still back in the old days, the more capable raid systems, under the attentive administrator, could bloat the size of the volume on command after creation.
Unfortunately this meant valuable storage space lay waiting for fulfillment, unused and spinning away, slowly warming the planet. The attentiveness of a storage administrator directly related to the grandness of the excess capacity. Excess capacity lying in wait for months if not years. Tsk tsk, certainly not efficient and hardly a candidate for a green earth award.
Now, imagine if that busy storage administrator could hire some minimally paid buddies – interns will do – huddled around a storage array console watching those storage volumes fill. Boring indeed, but being ever eager to please – hey those interns need to impress to get a full time offer – those interns could make a storage volume far smaller than requested, keeping that tidbit secret, in fact just big enough to satisfy current needs. I mean, come on, everybody asks for more than they need. Am I right? Let those interns click away to manually expand the volumes as they fill, keeping their secret intact. Put a game theme on that dull management console to keep it interesting. So now what do we have? Volumes, highly utilized expanding as necessary to fill the dynamic need.
That’s thin provisioning.
But you ask, I was hoping you would, what of all those unused disks that are still spinning warming the earth? Ah, those clever interns, driven to wear summer garb in the storage array confines, figured they could pull those unused disks, saving power, and lowering the haughty temps in their meager work space. Then just before anyone notices – the call goes out and disks are plugged in just-in-time. Living on the edge, there’s actually more space allocated than energized hardware to support it. Those sneaky interns. Problem solved, the volume utilization is now sky high, power consumption is tracking utilization, the equipment room is no longer a sauna and the only limit is space to plug in disks when the need arises. It’s a good world.
Thin provisioning doesn’t do procurement.
Thin provisioning, like our interns, allocates additional bytes “just-in-time”. Unlike those clever interns, it does not procure and energize hardware “just-in-time”. What’s the point of just-in-time allocation if the hardware is already sitting there powered up? Yes there are some convenience factors like not having to guess capacities but the real payoff, the reason to buy the technology, is to optimize hardware utilization. Procuring hardware on a just-in-time basis is a crucial part of the proposition. Those interns had it right – no sense powering the equipment if it’s not being used.
Offer those interns a full time job and get that automated thin provisioning system. There’s plenty to pick from with clever features like auto tiered storage, replication and the like. And once that spunky clean hardware is in place, ask the equally clever interns in the procurement department to land hardware as you need it. Never too late – you wouldn’t want to run out of space – but just-in-time.
[Posted by Gene Ruth]