I have a similar problem. I just started an 80gb transfer from e-sata to internal sata.
Speeds started above 130mb/s at 15mins to complete and within 5 mins has dropped to under 10mb/s with nearly 5hrs to complete. Following past performance, it should drop to as slow as 2mb/s.
I've got 3.5tb of other files to transfer back to my main drives (new raid array) and am up a certain creek without a certain instrument if the whole thing takes this long. I've seen this kind of issue on different machines, different OS and different drive qualities over the last few years.
For the record, I'm: Win7 64bit, Sabertooth x58, sata II, 2tb WD green transferring to one 7.5tb raid5 using wd greens. I know the raid5 factor should slow me down to some degree, but over a factor of 10?
File sizes range from several kb jpgs to dozen-gb avi files, just shy of ~20, 000 files total .
If I did a few gb at a time, transfer speeds tend to maintain in the 80+mb/s range. But shuttling tens of gb around, this slow down always happens.
The obvious solution is to go sub-folder by sub-folder. I'd rather chew my own foot off, I think. To my knowledge, all my drivers are up to date, all drives are set to raid, hard-disk write protect=disabled, ide detect time=35 secs(the max option).
Now at 5.25mb/s @ 21hrs to complete from 10mb/s @ 5hrs when I started typing this and sinking.
Edit: A few mins later, the speed dropped to 2.92mb/s and I noticed the freshly built, one-hour old raid had dropped a drive and was rebuilding at 0% done. I'm sure that could have an effect on the transfer process, but I've also seen this speed drop on other systems as well...
Edited by ModelersBrand - 11/18/12 at 6:24am