Datacenter cooling can be problematic in unexpected ways: NASA's Mission Control datacenter at the Johnson Space Center was an interesting beast - designed for

Datacenter cooling can be problematic in unexpected ways: NASA's Mission Control datacenter at the Johnson Space Center was an interesting beast - designed for the IBM vacuum tube behemoths of the 1960s, it was both huge in acreage (only a small corner was used by the '90s) as well as arctic in it's cooling capacity (since every tube literally had a heater in it!) In the mid-to-late '90s, working at Sun, I put in the first ATM and Fibre Channel networks in there, the latter initially connecting up a bunch of the new SPARCstorage arrays (30 individual disks per array unit!) to the brand new UltraSPARC servers. As I hinted earlier, the AC system was epic - literally cold enough to hang meat. It originally used several chillers, but even after turning off all but one, it was still FREEZING (well, nearly) in there - there was literally a rack of parkas hanging at the entrance, and you put one on if you were staying more than a couple of minutes. Not long after the system went in, we got a call from their admins saying there was something wrong with the network, as they couldn't get the Storage Arrays back up - sometimes. Eventually, a pattern emerged: the Arrays refused to restart after they had been shut down for more than an hour or two, but when we took them back to our office, they worked just fine. Turns out the problem was thermal: The room was so cold that the new state-of-the-art HDDs literally didn't have the torque to spin the platters up again against the cold-shrunk tolerances. We checked with Seagate and they said NASA was operating the disks well below their design temperature - they had never expected anyone to do that! The fix: 1) Don't shut the array down for too long, and, 2) if you really have to shut it down longer you'll have to wrap the whole array in plastic to prevent condensation, then take it outside to let the disks warm up enough before bringing it back into the DC and spinning up before the disks almost literally froze up again! This was, of course, duly written up in an official NASA policy and procedures manual. I suppose SSDs were a big win for NASA, as I expect the problem only got worse with succeeding generations of spinning drives....