Second External Drive Keeps Dropping Off

I never sleep my iMac or its HDs, just the display. Give that a shot and see if the problem goes away.

I've never replaced an ext HD. Do note, however, that if I'm not using them to update my bootable clones, I usually shut them off. I don't use TM or have any need for additional storage, since I don't collect photos, movies, or music. BTW, I have also disabled putting HDs to sleep.

But haven't I read that you had to replace an Internal? Unrelated to keeping it spinning 24/7? I know there's wear and tear from spinning up and down, heads parking etc., but aren't most drives rated to 50,000 spin up/down cycles? Would four or five such cycles a day be all that harmful? Not to mention the constant heat.

In other words, I'm curious to know your rationale for never sleeping.

Yes, the 1 TB internal on my 27" iMac went south, without any warning, not an uncommon issue with a small batch of the OEM ones from Seagate. However, the one on my mate's 24" iMac has been running w/o issues the past five years and it also runs 24/7. When inactive, there's no indication that the HD's writing or reading. Normally not awake for the machine's maintenance functions. Primary reason for electromagnetic devices to fail is the power surge at start up and the resultant warming up to a satisfactory operating temperature. Akin to light bulbs failing on startup, but not when constantly burning. Pondini offers this: http://pondini.org/OSX/Sleep.html for consideration.

Primary reason for electromagnetic devices to fail is the power surge at start up and the resultant warming up to a satisfactory operating temperature. Akin to light bulbs failing on startup, but not when constantly burning.

Hmm, I've heard that one before, but I'm skeptical. And not sure the light bulg analogy is really suitable. Even shut down, if still connected to power, there's trickle current going to the hardware, if I'm not mistaken. Anyway, there are posts from people who've shut down at night for ten years straight who've had no problems and then from users like you who swear by the opposite. A lot of this is just too anecdotal. I still need to see convincing statistics; and I don't think there are any.

And even if you're right about the startup power surge and temperature jolt to the drive, you'd still have to weigh in the possible negative of too much heat, too much of a good thing by never allowing it to sleep. Must also depend on ambient room temp. It was just 103 here (90+ inside) and I don't think I would have been helping the hardware last by not allowing the computer to sleep under those conditions.

Apple's recommendation to only shut down if the computer won't be used for a length of time and sleep otherwise is based more on the convenience factor. There's nothing in there about what's better for hardware.

Anyway, different strokes etc. Not something that will ever be settled definitively one way or the other. Probably a lot depends on the luck of the draw.

Btw, Seagate's are getting a reputation lately for being pretty crappy.

Sleeping will be the coolest (and shutdown won't be any cooler.) The next best as far as heat is concerned is to sleep the display (Ctrl-Shift-Eject), which removes the heat coming from the display. The fans keep running.

Most drives' upper temp limit is around 55C, but 45+ and things start to get somewhat concerning. I don't like to see the drive running for too long in the upper 40s.

http://www.codinghorror.com/blog/2006/12/hard-drive-temperatures-be-afraid.html

And there's smcFan Control.

http://www.eidac.de/

Baltwo probably won't agree, but, depending on room temperature, I don't think it's great news for the hardware to never let the computer sleep. Just my opinion and you're bound to find other ones.

But why don't you monitor the temps for a while set like that and post back with them--in Celsius please.

http://www.islayer.com/apps/istatpro/

Btw, with that setting to allow the drives to sleep when possible, I would have thought the externals would spin down. Or, their internal firmware isn't allowing that to happen and that setting is irrelevant for the externals. But that setting should allow the internal to spin down, which might not be bad for the drive if you're never letting the computer sleep.

Why those settings, which include allowing drives to sleep when possible, are keeping the second external from spinning down I have no idea.

I don't. I don't need any ext HD available when the displays sleeping, so these are my settings. Also, the temps are when fully operating. I've never bothered to capture them after the display slept overnight, since these are benign.

.

Follow up on the iMac HD replacement. I had mine done on 4/16 and Apple finally issued a recall on 7/22: http://www.apple.com/support/imac-harddrive/