On Tue, Jul 1, 2014 at 11:29 AM, Andras Horvath <[email protected]> wrote: > > I restarted copying again, and in a minute the CPU hung again with 100% I/O > wait. The "iotop" output shows absolutely nothing, as if there was no load on > the disks at all. Interrupt and context switch is around 20-50, so almost > nothing (dstat output). Disk operation is zero. Load is at 5.01. The rsync > processes that I'm using for the copy cannot be killed or force killed.
How much RAM does your system have? What does "/sbin/sysctl -a | grep vm.dirty" say? On machines with lots of RAM, I have seen disk subsystems act a bit squirrelly when Linux decides to buffer (say) a few gigabytes of writes. The traditional "vm.dirty_background_ratio" and "vm.dirty_ratio" settings are a percentage of RAM, which gives ludicrous behavior on modern big-memory boxes. Something like this is more sane: sysctl -w vm.dirty_background_bytes=67108864 sysctl -w vm.dirty_background_bytes=134217728 This is not terribly likely to help, but it is worth a shot. If the problem really is the disk spinning down, at least this will be more likely to keep it busy... - Pat
