July, 2010

How reliable your newest big hard drive is?

Who would have guessed that over 30 years that 5MB hard drive would grow to the 1TB and 2TB drives commonly used today? Reason to celebrate? Perhaps, but it is also a reason to take a moment for a sanity check. As with everything else, technological advances also have their pitfalls. Fortunately if we are aware of them we can take steps to protect ourselves.


Your typical hard drive, encased in a drive shuttle and strapped in next to other drives turning in the same direction can vibrate these heads. It doesn't take much movement to knock a head off 1/900th's the thickness of a piece of paper making it miss its target and forcing it to wait for the next pass. Miss the target enough and seek times go up, performance dies up to 80%. But there are a lot of other sources of vibrations around also.

But is this a real problem or just a mechanism for spreading fear, uncertainty, and doubt (FUD)? Of the 33 RAID drive enclosures tested, 11 were unacceptable for any drive, 21 were unacceptable for Nearline drives (the cheap and deep drives usually used in enterprise storage), and 28 were unacceptable for desktop class drives. Which enclosure are you using and where did it fall in this test? Since the manufacturers weren't listed you'll have to ask.

Enterprise drives tolerate the most vibration because of special technology that helps counteract head drift. Works pretty well too (but you've got to pay for it). Nearline drives are cheaper but they don't handle vibration very well (that's part of the pain you feel long after the joy of saving some money has dissipated).

As drives continue to inflate in capacity and increase in areal density enclosure vibration will become more of a problem to drive and data reliability. Why not ask your storage vendor how many rads/sec2 their drives vibrate? The dumb look on their faces might just be worth the extra money you'll pay for better drives.