[mythtv-users] Horrendous RAID-6 performance

[Enigma]

I occasionally have seen similar behavior with my RAID 6 array, it 
almost always has been a problem with an individual disk.  If one disk 
is misbehaving and the IDE layer has to wait for timeouts to be hit when 
writing to the disk it can kill performance.  The way I diagnose 
problems like this is with iostat, which on my Debian system is part of 
the sysstat package.  If you run something like

# iostat -x -k 5

and watch the await column, you should quickly be able to see if one of 
the disks is causing the wait states.