[Gabe86]

I have been having this issue on and off for about 2 weeks now.

I'll boot the machine and my work volume "INHS" won't appear on the desktop with the other drives. Then if I open disk utility sometimes it will mount the drive and sometimes it will show the manufacturer name on the list of drives but there will be a faded external drive icon below it with a generic label on it like "drive" with a digit after it. Essentially telling me that OSX is aware there is a physical drive connected to the machine but is unable to mount the logical partition on it for some reason. Sometimes OSX will sporadically dismount the drive and cough up an error saying that it was improperly ejected, as if I actually opened my machine while running and ripped the drive out. This also occurs after coming out of sleep. I'm not sure what this problem could be but it seems strange to me that it only happens to one of three drives in my machine.

So far I have booted from the SL disc and repaired all disks/permissions and reset the PRAM/VRAM at boot. It seems to have stabilized since the reset. The drive that unmounts is only a file drive, no OS installed on it or anything although it is formatted as extended (journaled).

Anybody had this issue before? What is the cause?

[reader50]

What is the SMART status for that drive? You can see this in Disk Utility if you click on the hardware icon for the drive.

It could be caused by an erratic cable connection, except your Mac Pro doesn't use cables. Try reseating the drive.

[Waragainstsleep]

Sounds like a flaky drive to me.

[Big Mac]

Yup. I experienced similar symptoms before a backup drive died outright.