Brian May <brian@microcomaustralia.com.au> writes:
I was running a unison sync to a remote ssh server, iotop was saying no (or low) disk I/O, top says up to 60% iowait, and basic tasks (e.g. clicking on xterm or selecting text in xterm) take ages (system appears to be frozen). Oh, and no swap being used, have 16GB ram with relatively few processes running. This seems to be typical.
iotop and iosnoop don't seem to report anything abnormal that I can see using the disk. There are cron jobs that run at times, however these problems occur with no cron jobs running (and basic cron jobs shouldn't kill a modern system in any case).
Not absolutely convinced this is a disk I/O problem, however something weird is happening here.
ionice -c3 unison on both hosts? Does the problem occur with rsync?