External Drive UNMOUNTING On Its Own...

Try a different cable.

Dave

I have the same problem with my 2nd internal HD, it just got unmounted - usually when TM back up kicked in. Error message showed up stating "device removal!"

Help

See my response in your other thread. Please don't double-post.

howwow wrote:
. . .
*Can temperature/heat be a cause for external drives to unmount suddenly? It was rather warm the past few nights and the external drive is very hot to the touch.*

I've never heard of it, but the drive may have a thermal protection, just as your Mac does. You might want to check with Iomega -- it's possible there's something wrong with it, even if it is brand-new.

*Is there such a thing as overtaxing the entire bus ports of FW400, FW800 and USB ports?*

I don't think so.

*Do they share the same power?*

It all comes from the same power supply in your Mac, but I think USB and F/W are separate. Your Mac will disconnect a USB port that's drawing too much power. I've never seen a post with a message about a F/W doing the same, but if the drive is drawing too much power, there's clearly something wrong with it.

I had this exact strange problem a while back with a new external drive I was using as an Airport Disk to throw Time Machine backups on over the network:

I turned out that the "one" physical drive/box, actually had two drivers in it (in RAID 0 I guess) so things would only start failing after enough backups had been made so as to fill the first one and start using the second one (which was faulty)!

Perhaps you can check the Console utility for error messages though what gave me a clue at the time was that the manufacturer's own "RAID Utility" would cause the drive to unmount/fail as well.

Have the drive checked by the vendor and/or replaced by your supplier.

François J. Perreault wrote:
I had this exact strange problem a while back with a new external drive I was using as an Airport Disk to throw Time Machine backups on over the network:

You need to know, backing-up that way, even to a "plain" external HD, is "iffy" and +*not supported by Apple.+* See: [Using Time Machine with an Airport Extreme Air Disk|http://web.me.com/pondini/Time_Machine/Airport.html] (or use the link in *User Tips* at the top of this forum).

I have also experienced this behavior with both a Western Digital external drive hooked up via FW800 to a 2008 MBP and a NewStack v3 connected to a 2009 Mac Mini via FW800. I have replaced both cables within the past month and still experience this behavior.

I don't recall this behavior before 10.6.4 although I cannot assign a cause.

I have this behavior when Time Machine is not set for either drive.

Out of interest this has recently started happening to me too. I have and Iomega drive I have been using successfully for time machine for 2 years or more. Recently it just unmounts. This happens regularly but not consistently and when it is successfully mounted it works fine.

I wonder if something in a new OS update has caused it.

J

I have no idea if it is a coincidence, but I noticed that after unmounting, iTunes had lost the library location in preferences. That is, there was no location set for the iTunes library which had been set to the external drive.

I've been having the same problem with an external drive that I designated as my Time Machine drive. I had a G-Tech 1TB external drive that would unmount from the desktop after I got messages from my system about an improperly ejected drive (I had not ejected the drive). This would happen at first after waking my computer from sleep, but then it would happen spontaneously and randomly while the computer was awake and in use. My initial response was to shut down the external drive and then turn it back on, after which it reappeared on my desktop, but the strange behavior returned a few days later. In my case, I contacted the drive's manufacturer because the drive was still covered by a warranty. The manufacturer told me that the drive was causing the system to send me warnings and that the drive was subsequently disappearing from the desktop (dismounting) because the drive had a faulty controller board. The manufacturer told me to return the faulty drive and it was replaced with an identical drive, but the replacement drive also failed - it also dismounted and sent warnings about improper drive ejection. I am now waiting for yet another replacement drive to arrive. The first failed drive was about a year old, and the replacement failed after one week.
Is it possible that your Iomega external drive has a faulty controller board, too?

Over the last few days, I have noticed this behaviour (external drive unmounting itself), but I have a 2TB Western Digital USB2 My Book Mac Edition drive that has been working fine with Apple's Backup program since I bought the drive exactly one month ago. The Backup files have now half-filled the drive, and when Backup is attempting to save a new file the drive unmounts and the backup fails. Hers is the backup log from Console for the last couple of days (Cassini is the name of the WD external drive):

2010-11-18 11:54:05.080 Backup[22672:8537] debug: unable to test mount disk image {
"image-components" = (
"/Volumes/Cassini/Backups/Phobos - 2010.11.18-00.30.22.847.backXX/Contents/Contents/Backup.sparseimage"
);
"shadow-file" = "(null)";
"system-entities" = "(null)";
}
2010-11-18 11:54:05.107 Backup[22672:8b03] unable to gzip /Volumes/Cassini/Backups/Phobos - 2010.11.18-00.30.22.847.backXX/Contents/backup.log: file does not exist
2010-11-19 08:42:53.803 Backup[22672:bb9f] debug: unable to rename disk image {
"image-components" = (
"/Volumes/Cassini/Backups/Phobos - 2010.11.19-07.36.08.399.backXX/Contents/Contents/311805478.972355.sparseimage"
);
"shadow-file" = "(null)";
"system-entities" = "(null)";
}
2010-11-19 08:42:53.848 Backup[22672:9e3f] unable to gzip /Volumes/Cassini/Backups/Phobos - 2010.11.19-07.36.08.399.backXX/Contents/backup.log: file does not exist