Imac sleep with external drive attached and time machine

[JoeBlow74]

I hope some of you Mac gods can answer a question I have. I have my 2011 iMac with Mountain Lion and a 2TB External Firewire 800 drive hooked up. I use Time Machine to back-up my iMac, But I have to leave both running 24/7. I know that I can allow both to enter into sleep mode, but how will this affect Time Machine? Can I allow both iMac and external drive to sleep and not affect Time Machine? While in sleep mode, will Time Machine still work it's magic. I would really like to get some answers.

 

[Brian33]

Yes, you can let both your iMac and the external drive sleep. Time Machine will not run while the iMac is asleep, but will run after you wake it up. That's the way it's designed to work. (TM will wake up "sleeping" hard drives whenever it needs to, so don't worry about them.)

Time Machine is really just a program, and no programs run while the Mac is in sleep mode. But, this really isn't a problem -- since no programs (nor the OS) is running, no files are being changed, and thus there's no need to run backups during sleep -- you're not missing anything.

An interesting side note might be *when* does TM run after system wake? On my 2008 iMac, it seems to start within 3 or 4 minutes, but on my 2011 MacBook Pro, it seems to start an hour after I wake up the machine. Don't know why the difference, as they're both running the same OS X 10.6.8 (Snow Leopard). Both seem acceptable to me.