I have a 2TB external drive with multiple partitions (thanks, Euan!) It has started dropping off the radar at no particular time - none of the partitions are being accessed when it does this- and I get the usual warning that it has been improperly closed down. I have then to turn it off and back on to re-boot. The other external drives do not do this fortunately. what may be the cause?
I guess the first thing to check is the power to the drive, e.g. Mains plug wiring and connection from power brick to the drive. Also check or replace the USB cable perhaps? A momentary disconnection in either cable could give the symptoms you describe.
You're right about the need to check connections Trevor. Such disturbances as you mention are collectively known as the Cleaning Lady Syndrome!
In this case they are checked every time the drive drops out and are found to be solid. The drive itself is parked at the back of the desk out of harms' way and doesn't move.
I've now noticed a further phenomenon - whereas six of the partitions (thanks Euan!) are shown with the yellow USB icon, the remaining two (even more thanks Euan!!) now have changed to the same silver icon as the Mac hard drive. Any reason for that? I have stuff on four of the partitiions and it is for two of the empty ones that the icon has changed.
Is the external drive connected by an eSata connection or USB. My eSata connected external drive occasionally drops off the system and needs a full power off on reboot. Given the randomness of the disconnection and the ability to reconnect without physically remaking the connections I think the problem is caused by the OS not giving enough time for the drive to reply to a request. I shall have to get an add on eSata card that allows hot swapping of drives.