I am trying to copy (actually a simple minded backup) 48 GB of picture files (20.000 files, typical size 4 MB) from a NAS file server to a USB external drive.
The original process was NAS -> ethernet -> PC -> USB drive
The transfer started quickly enough at 2.5 MBPS (as reported by the copy window of Nautilus) but rapidly slowed right down and eventually stopped after around 12 hours with about 6 GB transferred.
So I decided to make the copy simpler, and just copy to a normal ext4 partition on the PC.
Now I do : NAS -> ethernet -> PC
It started quickly, at 11.5 MBPS, but again the speed dropped quickly and stopped after about 90 mins with 4800 files of the 20.000 transferred.
The system monitor shows no obvious problem. I suspected some RAM or swap file problem but all looked good.
I'm running 12.10 on a homemade PC, AMD X3 cpu and 4GB RAM.
Any ideas what is going wrong? Where should I be looking?
BTW, this post is similar to "Copying speeds way too slow?", but sufficiently different.