Alec Shaner wrote: >Once the buffer fills up would you expect it to work fine at 1.2MB/s? I >wish I had kept the logs, but it was extremely slow (much slower than >1.2). I was copying a series of ~70MB files over and it would work fine >on about the first 5 or so files before croaking. I eventually had to >kill the job. > >
>From this, I'm guessing your machine has about 512MB of memory. The precise behavior I would expect is: The first 350-450MB of files (5-6 at 70MB each) would read at the speed the filesystem/disk can provide them...in this case it seems about 11MB/sec. So reading the first few files will take 30-40 seconds. At this point, the USB disk will only have written 30-40 MB to disk...leaving 300-400MB left to go. The userspace program (rsync,cp?) at this point will basically stop writing for the next 5 to 7 _minutes_. In other words, you will not see nice smooth transition from 11MB/sec down to 1.2MB/s. It will burst at high-speed for several seconds, then stop for an extended period of time, before resuming again. This of course assumes that there are no hardware problems involved. You may want to check your /var/log/messages file or dmesg output for any timeout or other disk errors being reported during the copy operation. The kernel's reaction to a communication error with a disk is to reset the controller and retry the command. I'm not sure if there is an eventual timeout to this process or not...if there is, it is larger than my personal 'patience timeout'! ;-> -Richard -- gentoo-user@gentoo.org mailing list
