Caveat: I’ve not got proof of what I’m about to say, but the circumstantials are reasonable. YMMV.
The other day the power went out around here. No problem, since I have several UPS’s guarding the electronics, so I finished up what I was doing, and shut off the computer.
But I made a mistake in failing to shut off the UPS’s as well, once everything was shut down. Thing is, everything wasn’t shut down. I keep a OWC FW800 two-drive bay running all the time… but I moved it under the house because the noise of it (& its fan) drove me batty.
So, there it was, merrily spinning away… ready and willing to accept my next Time Machine backup.
I blithely just closed the door, so I wouldn’t hear the beeping of the UPS-en, and headed off to the couch to read, and nap. Naturally enough, during the hours that the power was off, the UPS keeping the drive, and its power-brick, alive eventually gave up.
Later, when the electricity was restored, I discovered the error of my ways (at least one of them, anyhow): I really didn’t want the UPS to sputter out like that.
For one thing, it killed my power brick for the drive. This I can attest to, since it didn’t have enough go-juice left to spin up the drives anymore, and a replacement power-brick worked just fine.
But moreover, (here’s what I -suspect-): it didn’t do the drives any good either. I decided to run SMART Utility on them, and one drive reported a remapped sector, and the other drive reported 32 of them. Big warning flags: drive(s) is failing!
Yeah… but… the drives have only 4200 hours on them – about 1/4 of their expected life, and well past the “child-breakdown” stage.
So, my suspicion is that TM was running and writing to the drive with 32 errors at the time the brick started getting weaker; wacked; and supplying god-only-knows what kind of power to the unit.
In short: I’m currently running on the >theory< that the 32 remapped sectors drive is, in fact, NOT going out, but suffered from problems associated with my stupidity in letting the UPS grow weaker and weaker, resulting in a burned out power-brick, and the errors on the drive.
I could, of course, easily be wrong, and be ever-more the fool for putting that drive back in service (albeit with expendable data) now that I have a replacement brick.
But at the very least, I do feel that a caution is necessary regarding power-bricks hooked up to a UPS.
Based on this one anecdote, I’ll be changing my behavior, and when the power goes out, and the UPS kicks in, I’ll be sure to turn off everything, and then turn off the UPS!