FireWire issues with external drive in Yosemite
I have just upgraded to OS X Yosemite, and I have an annoying problem with my 500GB FireWire external drive (which I use for Time Machine backups).
Basically, after updating the drive won't show up anymore, neither in the Finder nor in the Disk Utility. I also tried the "diskutil list" command in the Terminal, but it is nowhere to be found. Note that the drive does indeed receive power from the port - it spins - and when I look into System Report --> Hardware --> FireWire it does show up there (but I can't mount it). Furthermore, if I use a USB cable to connect the drive everything works fine, so the disk itself seems to be OK.
The funny thing is that if I boot with the drive plugged in the FireWire port the system mounts it normally. But as soon as I eject the drive, I am unable to mount it again (unless I switch to the USB cable, as mentioned above).
Prior to the update, everything worked flawlessly. For now, I backed up my Mac via USB 2.0, but it's very slow and I definitely don't want to resort to this workaround everytime. And it goes without saying that I don't like having issues with my primary backup device in general.
I already did all the usual troubleshooting (rebooting, resetting NVRAM and SMC, ...), but the problem still persists.
Any suggestion?
MacBook Pro (17-inch Mid 2009), OS X Yosemite (10.10)