We have a busy server, chocking under a high IO load, at least, that's the feeling I have. Output from
iostat -xz looks like this:
extended device statistics device r/s w/s kr/s kw/s wait actv svc_t %w %b sd5 224.8 157.8 10701.8 6114.7 0.0 9.5 24.7 0 100 sd5 243.2 110.4 11565.3 4065.0 0.0 9.7 27.5 0 100
It's obvious that the disk subsystem is overloaded, since a 25ms service time is unacceptable for a 6 drive SATA array, and a 100% busy also means we're chocked on disk IO.
But - why is
0.0? And why is
%w is also 0?
%w sometimes goes to
1, and quickly returns to
Doesn't this mean that no process is waiting for IO?
Does the RAID controller somehow causes this result / masks the wait times?
Can someone explain this behavior?