In my courses on data center energy efficiency, we touch, too briefly, upon data storage technologies that can reduce energy use. I say too briefly because data storage growth rates vastly exceed compute growth, and in my mind not enough attention is paid to the half dozen or so energy efficiency measures and best practices.
One of my more enjoyable anecdotes was to talk about MAID storage. The technology was pioneered by Copan about five years ago, and despite a similar offering from Hitachi, it hasn't seemed to gain any traction in the market.
MAID systems are really all about controlling disk drives - a software front end determines whether the data to be stored will be accessed often or rarely. The rarely-accessed data is stored to disk drives that are then shut down - you can get the data again, though it takes a little longer to get to it as the drive has to be spun back up.
A brilliant system and very easy to see the efficiency gain: in Copan's system no more than a quarter of the drives could be on at any time, so energy savings was 75% compared to normal cabinet full of drives.
The anecdote was that Facebook was an early adopter of the technology, so that meant that the profiles of unpopular people were being sent to the idle disks, while popular people had profiles on live disks. Funny! Of course in reality Facebook was probably simply saving older posts to the idle disks, as people don't really search back very far in profiles.
Now comes word through DatacenterDynamics Focus (page 64 of the current issue, subscribe here) that Facebook has brought the MAID concept in house, though in a new way. Facebook now sends little-accessed data to "cold storage" - disks that are turned off, but also housed in a separate data center.
The use of a separate data center makes a lot of sense when you think about it. There is no need for backup power for the cold storage racks; no UPS, no generators. The racks likely need far less cooling capacity than "standard" storage or compute racks too.
Will this approach work for enterprise data center operators? I don't think so - it's a pretty customized solution that will work for large-scale operators like managed services and cloud computing sites, but I doubt many enterprise users will be able to justify dedicated data storage sites. And again, it doesn't look like the MAID solution has any traction at all.
I expect that solid state storage solutions will be the primary go-to for enterprise applications, along with data management measures (deduplication, compression, thin-provisioning, etc.).
Now let me get back to reworking that anecdote...