I have two external HDDs, both directly connected by FireWire to the iMac (not daisy chained). The Lacie d2 Extreme holds my iTunes library, and the Seagate Freeagent Desk handles Time Machine backups. I noticed today that neither were mounted, and spent an unhappy hour or two when I should have been working trying to figure out why. Shutting everything down and then powering up the Mac, followed by the drives and then connecting them to the computer resulted in the Seagate drive mounting, but then ejecting itself within a minute or two with the attendant warning message. The Lacie wouldn't mount at all, and neither drive could be detected in System Profiler.
I tried the Lacie drive on my MacBook Pro and it wouldn't mount on that either, but I noticed that the power supply was buzzing. Did a search on this, and found that these power supplies are very short lived, and if they are buzzing, the drive won't mount. I've since plugged the Seagate back in on its own and all seems to be well with that again. It mounted fine and after an hour or so it hasn't ejected itself.
It would seem that a problem with one drive could well affect the performance of another, even if they have their own connections. Could this be the cause of the problems that some of you are having, particularly those with more than one drive or device connected? I will be ordering another power supply for the Lacie drive and hopefully it will be fine again. I hope so - I've about 120Gb of files on there!
Message was edited by: Roger Green
Message was edited by: Roger Green