Currently Being ModeratedJan 13, 2013 2:43 AM (in response to bridgwater)
Well I found a fix at least for my problem with an external drive.
I had to do a full shut down of the iMac today to move it. When I switched back on the WD 500Gb loaded and started backing up!
Its a bit of a *** to do but at leat Time Machine is now working.
Currently Being ModeratedJan 18, 2013 12:27 PM (in response to iamapple)
I had the exact same issue and resetting the SMC fixed it. I shut down my laptop, then I held down control+shift+option and pushed the power button. Nothing should happen visibly. But, it has reset the SMC. This fixed my issue and the drive is accessible now. This was on a 2012 Retina model, so it made power nap work again.
Currently Being ModeratedJan 19, 2013 9:26 AM (in response to jkeefe)
but no go I am afraid. Same problem if you put the Mac to sleep when it wakes up it has had amnesia and completely forgotten its got a time machine hard drive attached.
Works fine when I shut down and re-boot though. So I will use that work around until Apple get their collective finger out and come up with a solution
Currently Being ModeratedJan 19, 2013 9:56 AM (in response to iamapple)
Just to let you know that this problem depends on the drive model and on the interface (usb3/TB) used.
On my imac late 2012 it works flawlessly with my WDC Thunderbolt duo 4To and same with a Lacie rugged 500gb usb3 self-powered. They both remount nicely on wakeup without error message
Currently Being ModeratedJan 21, 2013 12:13 PM (in response to cybercap)
Thanks to all for the useful comments and suggestions. I gave up and returned the unit to Amazon for a refund. Powered drives appear to be the route to go. I only need a 500Gb drive and non-portable.
I'll look into the Lacie rugged 500Gb mentioned by cybercap
Currently Being ModeratedJan 21, 2013 6:48 PM (in response to iamapple)
I have been having the same issue with my new 3tb Toshiba External connected to My MacBookPro and/or my iMac (tested on both) would dismount when the computer sleeps for 2 hours or more. I was connecting the drive thru a powered usb hub (dlink).
When using the hub the external would eject after 2 to 3 hours of the computer sleeping. When connected directly to the computer the drive would stay mounted after waking my mac/s from sleep. No more annoying message when I wake my mac/s.
I have no choice but to use a hub, as I have many external usb devices. So I needed to swap a few things around to get the external on one of the ports of my mac/s.
Going to system prefs and unchecking putting the hard disk to sleep is only for the internal drive. So this does not work!
Remember: Time Machines function better when connected directly to the mac, do not use a hub (even if it's powered)....
Currently Being ModeratedJan 25, 2013 10:09 PM (in response to wclyffe)
I posted earlier here, but to make it easy I'm using an OWC Elite Pro HD for Time Machine and backing up via Firewire 800 directly plugged into my new MacBook Pro running OS 10.8.2. Of course, my external hard drive keeps disconnecting when the computer sleeps and it gives the "improper ejecting" message.
My question though just occurred to me: When I put my computer to sleep, or it just goes to sleep on its own, the small light in the front glows brighter then fades and does this for awhile. But after some time that light goes out and is completely dark. Is this normal? And is this possibly the point at which the hard drive might be disconnecting from the computer?
Currently Being ModeratedJan 26, 2013 6:59 AM (in response to wclyffe)
I 2 have external Buffalo HDDs both of which are mains powered and plugged directly into my iMac, but I still get the error messages, but sporaddically.
Sometimes its everytime I wake it, other times it can go 4 or 5 days before I get the error, there seems to be no pattern to it
Currently Being ModeratedJan 26, 2013 1:15 PM (in response to wclyffe)
The light on the front of the computer goes bright and then dim in a cycle to indicate that the computer is on. When the light goes out, the computer has died and you'll have to re-start it. I think you should give some thought to the idea that you may have multiple problems - software problems, to be specific. I found, after weeks of scratching my head, that Mariner Write was causing my computer to spontaneously re-boot. I have solved my external drive problems by plugging the drive directly into the computer and my re-booting problems have stopped ever since I got rid of Mariner Write. It isn't easy to isolate these problems, but Apple sure as **** isn't going to provide any assistance. You'll have to analyze the problem and approach it one step at a time. Best of luck to you!!
Currently Being ModeratedJan 26, 2013 4:35 PM (in response to Pisonia)
Actually, after the light goes completely dark the computer can wake quite fast when I open it up. I think it's going into hibernation mode, but I'm wondering if that's where the external HD is being improperly ejected. I have Macsales looking into it with respect to their HD, but for the moment I'm stuck doing manual backups.
Currently Being ModeratedJan 27, 2013 6:51 AM (in response to Pisonia)
I've noticed that after the MacbookPro sleeps (light glowing & dimming) for two hours the light then goes dark completely. Is this normal or should it still continue to glow? I have plenty of power left on the battery, but if it is a software issue I'll have to start a process of elimination. My only issue is the improper ejecting external hard drive.
Currently Being ModeratedFeb 4, 2013 2:18 PM (in response to wclyffe)
Having the same thing happen with a new iMac 27 and a 1.5 TB Fantom Green Drive. Disconnects immediately after sleeping so can only use it with Time Machine if it never sleeps. Has to be some explanation for this. I wonder about keeping a list of drives that do disconnect when the iMac goes to sleep.
Currently Being ModeratedFeb 4, 2013 2:31 PM (in response to davidra)
I'm using a DROBO 5D with 5 x 3TB drives. It's partitioned ( using Apple Disk Utility) and I have, for Time Machine, an 8 TB volume. The DROBO seems to wake when Time Machine needs to be updated. It also wakes when my timed backups (to a different partition) are carried out via Synchronise Pro. So, I can recommend this type of approach if you need backups to TM or a bootable partition.
Currently Being ModeratedFeb 4, 2013 3:15 PM (in response to wclyffe)
Sorry for the late reply, Wclyff - I kept forgetting to look at the light before striking a key to wake up the monitor. I've looked at the machine after it has been asleep over night and the light is still going bright and dim. If the light isn't lit, to me, that is a sign that the machine has shut down. That's how it worked for me, at least. It seems as though this issue manifests itself differently on different machines, so I don't know what to say, really. I do know that the SMC and NVRAM reset seemed to fix my problem. In the meantime, if anyone asks me about upgrading to ML, I tell them not to do it. Not until Apple addresses all of these quirky issues and finds a solution for them.
Currently Being ModeratedFeb 4, 2013 4:34 PM (in response to richardjamesc)
I tried the same drive with my son's Mac Pro. It did not disconnect when put to sleep. I noticed something else, and as a Mac newbie I'm not sure if this is usual behavior; when we put his Pro to sleep it took a minute or so to shut down the screen. On my iMac the screen immediately goes black when I click the "sleep" option. Is that normal for a new iMac 27"?