Hi,
This problem doesn't seem to get any real attention and we're nowhere from a real resolution ! (Just look at the dates of the many posts).
I'm on a PBG4-1.67GHz-17" (that's a good old PPC) with MOSX10.5.8 with all the Software Updates installed from online to the current day. BTW this is a bad PPC OS release, and a sad place to strand faithfull users still using PPC on Apple's part !
I've started to experience slowness of external drives WD MyBook 1Ti, 2Ti, 4Ti no RAID/RAID according to models. I use all of those in FW800 for obvious speed reasons. Now file copy between external drives and between Mac and external takes AGES even for chunks of 2Mi ! And now my WD started to self unmount for no visible reason too.
A fresh reboot, then connect FW800 MyBook : it mounts (quite slowly too) and within 5 seconds of it's icon appearing in the Finder as mounted, it disappears because it gets ejected. Sometimes I get the OS message "Incorrect device removal" but not always !
When I retry to mount the WD, it dos NOT appear to have suffered any abrupt unmount, I can't perceive that any fsck is being performed by OS.
I can't seem to find anything useful in Console.
I've the same problems regardless of the fact that I connect WD drives one at a time to my Mac or in daisy chain !
I used to connect in daisy chain, of course, since FW is designed to work that way, and I had no problem before.
I don't have TimeMachine set up on this machine and nothing else is connected to it.
I've tried swapping cables between the WD drives and have tried 2 extras cables from Belkin.
I also tried reinstalling a fresh OS and booting clean before attempting to use the drives.
DiskUtility and WD RAID Manager are happy with the drives.
The drives and Mac are not overheating since I get the problem regardless the uptime of the systems/devices.
Other forums I've read about this problem report this happening with/without TM, iCal, iSync, USB2, Intel-based Macs : many reports but NO resolution.
For what I can gather reading all the posts I found is this :
I avoid USB so I can't discuss USB.
Apple Mac PPC/Intel vs multiple brands of FW drives and multiple cables tested.
I don't think it has to do with TimeMachine and there's very few chances it has to do with iCal or iSync or even EnergySaver or ScreenSaver settings either.
If everybody reported about WD drives only, I'd say there may be a conflict between WD's RAID Manager "plugin" (different versions get auto-installed when various MyBook devices are connected, and they seem to run in parallel (when daisy chained devices are used) ... !?
? under the same icon in the Finder Menu bar, but there could be an instance running per drive by design from WD ... )
But people report also using other brands.
This all points to OS/FW issues to me, regardless of drive brands and other software running (other than drivers/drive tools such as WD's RAID Manager I mean).
I wish someone at Apple or one of the drive brands would communicate on this.
Hoping for some answers,
Bye.