Q: Anyone else having problems with external disks unmounting randomly/suddenly on Mavericks?

Did you connect via a USB 3 enclosure.  If you did try changing the cable to a USB 2 one.  This worked for me.

Per Mark Ashworth's suggestion, I have changed from a USB3 to a USB2 cable.  My backup is running now and seems to be OK.  Thanks very much!!!

same here under 10.9.1:

2 external usb 3.0 SSD´s not remounting after sleep, but occasionally, not very often.

what can i do please?

Middle of January, and this problem is still here.. Can't back up to Time Machine drive.. tried an external Thermaltake drive housing, and it fails the parition process on three different working drives.

Seriously, Apple... this is our data we are talking about.. NOTHING is more important... Why complete silence?

I can't try a usb 2.0 cable on either as the connector is different.

I have 1000.00 in hard drives sitting here that I can't use.

Has anyone taken their mac in to the geniuses yet to have them duplicate the problem?

Same problem here.

500Gb Freecom on USB 2.0 won't stay connected for more than 15 minutes (20" i5 iMac).

Only started happening under Mavericks.

Reading more last night... pretty shocked right now..

I found another usb 3.0 cable from a friend's external drive unit... Time Machine Backup is up to 60GB  (always failed before 20)

Could this actually be the problem?  (note.. I have TWO usb cables on TWO different drives that failed) granted these were older units, and the new cable is from a new Drive)

Is it possible there is a new spec or changes to USB 3.0 cables in the last year?

Will test this cable on other drive that failed and will report back.

Others have reported success going back to a usb 2.0 cable, but I havent found any posts about using a replacement 3.0 cable...  Hope this is the magic bullet we all have been waiting for.

Both drives have now backed up 120 GB of data using new cable on a Thermaltake BlackX5G Usb 3.0. WITHOUT disconnecting, using the NEW USB 3.0 cable from a LACIE P9233 external drive.

These are the only changes I made from last night (not even a restart).

Try replacing your USB 3.0 cables to a new one/different one and see if it fixes what ails you.

BTW the second drive was a SEAGATE 2 TB GOFLEX drive that i removed from it's casing and plugged into the Thermaltake....

Which proves to me that it is NOT THE SEAGATE DRIVE failing as the other posts seem to tell us.. it is the casing/cable causing the problems, not the drive itself.

It is backing quickly and without fail..

Hope it helps someone else.

I obviously don't know what the full set of problems is, but I have a brand new (October 2013) Thunderbolt connected LaCie RAID, so it's not just a problem with a USB cable.

I found the problem got much less frequent (but did not go away, unfortunately) once I started the initial Backblaze (online backup service) backup, I think because this means the disks are almost non-stop active, even when I'm not sitting at the keyboard.

However, it isn't just when the computer is sleeping (I've had it happen while I was working), it isn't just USB or another connector type.

Apple really needs to figure this out and get a fix - other than reporting the problem in their feedback section (which I did ages ago as suggested in an earlier post here) what else will make them pay some (any?) attention to this critical problem?

It really feels bad being effectively abandonded with this serious problem. Not at all the sort of thing you expect from Apple.

I had a prior post that, it's not only external disks, but also my Canon Imageformula P-208 - a portable mini scanner that is connected to my brand new iMac.  I randomly get double disconnect messages ("disk not properly ejected) even when the Mac is not in sleep mode.  This is a deeper OS issue concerning peripherals connected through USB.

That is just not appropriate for no response from Apple.. I mean if it was simply a webcam haha or something ..no REAL biggie...but this is our data we are talking about.

I will say I'be been backing up all day to various drives that did not work yesterday, and still no problems of "unmounting" which happened every 5 mins yesterday.

Jsnover, any chance your drive has a uSB 3.0 connection as well as Thunderbolt?  that would be nice to see if that worked or made any changes.

I have put the never sleep setting on for the computer and that seems to have solved the problem.  Of course, probably not an ideal solution from a cost or wear and teat stnadpoint, but at least there have been no random ejections.  I am puzzled by Apple's silence in this matter.

true that... that was my first step.. then , then then, then, haha.. applecare said reinstall Mav... drive failed in 4 mins after that.

I can tell you what has worked for me so far. I lost 3 drives to this and I mean completely lost as in they would no longer mount or reformat. Two of the 3 were under warranty and were replaced.

I reformatted my drives under Mavericks and have not had any issues since...knocking on wood here.

I do wonder why Apple has not addressed this issue, it is prevalent, obviously. Good luck!

it seems that apple has issues with sleep since years.

the ssd´s are getting destroyed by not ejecting them properly, i ve heard.

since 10.9, when my imac goes to sleep (and my mbair) the external usb 3.0 discs (ssd)

are not ejected before sleep, and i had this warning several times.

workaround:

i installed "jettison", now the app ejects all discs and remounts them. works fine so far.

i wonder why osx needs this app to do a simply task.

That's true..sleep issues have been with us a very long time. I actually installed "Jettison" which has helped, but only if i put the machine to sleep manually via the menu bar app. I have 3 different drives connected to my system, 2 via USB3 and a Drobo Via Thunderbolt. The Drobo is the only one that gives me trouble with the "did not eject disk properly" dialog as well as the drive not showing up on the desktop occasionally. It all started like everyone else on the day I upgraded to 10.9.