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Steppy 11-03-2011 04:51 AM

External Time Machine HDD Does Not Sleep

I've had my iMac now since September and I am loving it, but I have a couple of questions below. I did try searching, but most of the results were about Macbooks.

I use a 1TB Buffalo external USB drive for my Time Machine backup which has worked great so far. It used to live under my desk tucked away, but recently I have moved it into a ventilated under desk cupboard so I don't keep hearing it spin up and seek when it backs up. I realised this morning when I went to get something out of the cupboard that it was still running even though my iMac was in Sleep mode.

The power/seek green light was off, but the drive was spinning and was therefore slightly warm to the touch.

I can't be 100% sure, but I thought it used to shutdown fully before. Also my iMac never seems to go to sleep automatically anymore.... could the two be connected?

Is the drive going to be consuming much power and will it do any harm?

BTW I am running OSX Lion

The other question, what happens if I switch off the power at the wall when the iMac is sleeping.... does it harm anything?

Thank you.

chscag 11-03-2011 01:53 PM

Some external hard drives will prevent your Mac from entering sleep mode - it just depends on the drive's firmware. A constantly spinning hard drive is consuming energy and will wear out faster.

My personal rule is I never leave my hard drives attached to my iMac unless I'm actively using them. And that also goes for my Time Machine backup drive as well. However, that may not work for everyone especially if you forget to attach the TM drive to make the backup. I use Time Machine every 2 or 3 days to do a backup rather than the default every hour which in my opinion is overkill. But I also use Carbon Copy Cloner every 2 days to clone my hard drive to another external.

To answer you last question... Don't switch off your iMac when it's sleeping as that can mess up its brain and may corrupt data. Also as an aside, I highly recommend using an UPS with your iMac.

osxx 11-03-2011 01:56 PM

To add to what chscag said make sure your drive has the latest firmware by going to Buffalo's site.

Steppy 11-03-2011 02:14 PM

Thank you both very much for your replies. I am glad I never did the switch off at the wall which I have been very tempted to do.

Funnily enough when I got home tonight the drive was off and cool. Maybe it had come on in the night and hadn't yet shutdown :\

I will check the Buffalo website to see if there is an updated firmware.

My Mac used to goto sleep on its own, but not anymore. I did read somewhere that home sharing could stop it sleeping, but not sure if thats my problem.

Thanks again for your help

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