On Tue, 13 Jul 2010, Elvedin Trnjanin wrote: > For USB transfers, every read/write goes through the CPU so an external > USB to another external USB doubles the CPU load. And with two cores, I use up both cores. That was what it felt like, but I'll tell you two weird things about it: (1) the ps aux and top output both showed no major CPU usage (2) it was almost as bad when downloading files to one of the two drives (3) uploading files from a drive had no major effect on user experience In other words, it was the writing to one drive that was killing me, not the reading from the other drive. I just tried downloading to the other drive. The experience was the same -- it was OK for 1-2 minutes and then the system slowed way, way down. So the problem is not with the one drive or the USB port it is connected to. I'm using scp for these downloads/uploads. I was using cp for the local copying. I was copying a fairly large number of medium-sized files (just a dozen megabytes, max, per file). Mike