iMac won't sleep

New iMac owner here. Love it. I'm learning FCP currently and could not be happier with my Mac. Anyway I'm having a hard time getting it to stay asleep. I put it in sleep mode only to find it awake with my hard drives spinning away when I return. I've got a 1TB internal drive and two 1TB external drives. I've tried turning of time machine b/c I thought that might be waking my mac. I've run out of ideas as to why this is happening.

Do you leave the external drives attached 24\7? Some external drives do not pay attention to the "Put hard disks to sleep when possible" command. That would definitely wake the iMac up. I've got several external drives that act that way. You do know that you can set Time Machine up on a schedule and have it only backup when the drive is attached?

chscag said:

Do you leave the external drives attached 24\7? Some external drives do not pay attention to the "Put hard disks to sleep when possible" command. That would definitely wake the iMac up. I've got several external drives that act that way. You do know that you can set Time Machine up on a schedule and have it only backup when the drive is attached?

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according to this, do you know where can i set up external hard disk to sleep

thanhdao said:

according to this, do you know where can i set up external hard disk to sleep

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System Preferences -> Energy Saver -> Power Adapter. Place a check in the box that states: "Put the hard disk(s)........." Note my reply above, not all external hard disks can be put to sleep.

Also check your "wake mac with mouse" settings. I found my magic mouse was a tad sensitive, and sometimes my Mac would wake up. When I changed this setting, it seems to stay asleep... at least in my account.

Now, my wife's account seems to have something that every now and again, still seems to wake the Mac. I have changed the mouse setting for wake, and it still happens. I am wondering if it is something like an alert in calendar, but have yet to find it.