For all the fussing about making servers more energy efficient, storage is destined to be the big green headache over the next five years.   More individuals and businesses alike are using mobile solutions, sharing and saving more stuff in "the cloud."  All that stuff is going to end up being spread around for back up in a gazillion different schemes.  Adding on all the new ways to collect and process audio and visual data is going to end up with storage outweighing compute at some point in the future.

Before I start rolling out the nightmares of storage, let me close the issue of compute power being the "long pole" of consumption in green data centers.  We'll start at the physical layers, with hardware manufactures get better at building more power efficient servers through a combination of improved industry-standard (i.e. the latest multi-core Intel silicon) CPUs and tweaks in design.  Facebook's Open Compute initiative is adding more efficiencies by re-imagining server, rack, and data center designs.  We're also going to see ARM-based designs start to gain favor once 64-bit versions of the CPU start shipping.

All of this goes on before software improvements.   Virtualization, depending on who you talk to, has barely scratched the surface of "retiring" older, single-function servers.  As newer, more powerful hardware is purchased, virtualization options will be integrated, so one server can roll in and replace anywhere from 4 to 20 older servers at a time.  Lower-power, standby/(almost) instant-on server technology is a little farther off, but is an obvious next step for delivering compute "surge" capacity.

Storage solutions aren't gaining as quickly. Disk drive capacities continue to increase, but everyone is moving to the cloud.  Many people (myself included) are spreading out personal storage across multiple "free" services, so there's a lot of waste happening already.  Every year, camera phones get more megapixels to take still images and videos and those images are getting shared more frequently through iCloud/Dropbox/SkyDrive services.   There's also the march of digital video cameras supporting full HD video -- whatever THAT means this week  -- so start adding more petabytes to your future estimates.

Don't look to the chip industry to solve explosive growth.  Solid-state drives are still expensive and have comparatively  limited lifetimes when frequently used.

Another area I'm willing to bet adds onto the growth of storage is voice.  Yes, boring, shoved-under-the-doormat voice.  As phone systems around the globe move to IP, it's easy to record voice.  More businesses are going to start recording all of their inbound voice calls so they can start mining all of those customer and partner interactions for sales and marketing data.  

Large call centers have been using voice analytics solutions for years to convert calls into searchable text and then spot emerging patterns in the markets they serve.  The emergence of HD voice -- higher quality sound, larger files to store -- will enable more sophisticated voice processing services  to crunch voice calls for management metrics, customer service efficiency, competitive intelligence and areas I can only begin to imagine.

Oracle has started promoting a concept called "HyperVoice," the ability to index recorded phone conversations and then go search them for key phrases.  To store one conversation should include the original conversation, the speech-to-text conversion, and the index file. Multiple by tens to hundreds of calls a day times the number of employees times the number of days of business operation and the storage numbers start to add up very quickly.

Businesses will be the first to fully embrace recording all inbound and outbound calls, but there's nothing to say younger, Facebook-enabled, no-privacy(shame) generations will consider having personal call recording to be just another feature so they can remember what they told their friends or what Mom and Dad asked them to bring to Thanksgiving dinner.

So if you want to stay up late at night worrying about green data center issues, start to worry about storage.  Unlike computing, there's so easy path to saving energy with growing demand for more cloud storage only continuing to grow in the years to come.