Tight Squeeze: EMC Joins The High Density Storage Brigade

Back in the Twentieth century the increase in disk drive bit density allowed us to keep up with growing data sets by periodically replacing disk arrays with ones using drives that hold 4-8 times the data in the same space. Lately the data we have to store has been growing faster than disk drive capacity, and as a result, vendors have been experimenting with high density arrays packing more drives in the same space. This week EMC threw their hat in the ring with a double-deep rack for Clariion mid-range arrays.

EMC's managed to get four times the density out of their new Clariion by stacking twice as many DAEs (EMC's current Fibre Channel JBODs) in a special, deeper EMC rack and stuffing them full of 2TB drives that can spin at 7200 or 5400 RPM. The DAEs are mounted one behind the other on special slides that include a channel, in black in the photo to the left, to route the front unit's power and data cables safely past the "backseat driver." The EMC folks say there's just enough space between the two shelves to remove a drive from the rear shelf, but it looks like a knuckle-buster to me.

The downside to this arrangement is that the rear shelf of drives is breathing in the heated air the front unit is blowing out so it's going to run a little hotter than if it were sucking in cold aisle air. When they told me they were putting two DAEs in a row, I was expecting a front and back mounting with a chimney to exhaust hot air out the top. EMC's also bucking what looked like a trend, as several vendors, including Nexsan, Data Direct Networks and Dell/Equallogic, have systems holding more than 40 drives in a 4u top loading shelf. The biggest problem with top loaders is that you have to pull the whole 120+LB shelf out to open the top and swap a drive. Mounting a full 40+ drive array is a two-man job even with a Genie Lift. If a lift isn't available, I pull the drives and power supplies to get the mass down something two guys can handle without serious injury.

Those building storage systems based on server motherboards, like FalconStor's NSS or NexentaStor turning the server into an iSCSI array or Data Domain, Sepaton or any of the other backup target/VTL vendors, can use new cabinets from SuperMicro that mount 24 hot swap drives in the front and another 12 from the back in a 4u case with interior space comparable to a 2u case for expansion cards and such.

Note that a full rack of these high density systems can tip the scales on the north side of 1500 pounds. That means one rack of 10 SATA beasts generates a floor loading of 250lbs/sq. ft., which could be more than your floors can handle. I recommend a conversation with your facilities folks, or even your landlord, to ensure the five racks of high density storage you want won't end up in the office downstairs just as you finish migrating your data to them.