Hello
Original question:
> >I have a question about saroutput. We have a Sparsserver 2000 with 6 cpu.
> >On the machine there is one process that do a lot of I/O on one disk.
> >The other processes don't need this disk and do not a lot of I/O. The sar
> >output give us that %idle is about +/- 8 % and waiting for I/O completion
> >is 70%.
> >
> >vmstat 5 give us a idle time about 60 %.
> >Normally, I expect that sar output should be about idle time +/- 50 %
> >and %wio +/- 10 % (for the one process that do a lot of I/O)
> >
> >Give program 'sar' us a wrong output or I do a wrong interpretation ??
1. The sar -u output is in sync with vmstat 5 output You may
want to run "sar -u 5 100," "vmstat 5," and "iostat -tx 5" at the
same time.
2. The id column in vmstat 5 output is the sum of %wio and %idle in
sar -u
3. Because of only one process doing a lot of I/O and your SPARCcenter
2000 with, I imagine, more than one processor, "mpstat 5" may be a
better tool than vmstat 5.
The definition of % waiting for I/O completion means that 70% of the time,
there is at least one process waiting for I/O, and *no other runnable
processes* in the same time interval.
There is one thing that is rare. There is one process that use
a lot of I/O but all processors have % waiting about 70 %. Is that
normal ?
Thanks Birger A. Wathne and Anchi Zhang
Touquet Geert
--
--
Geert Touquet E-mail : Geert.Touquet@uz.kuleuven.ac.be
Mail : Universitaire Ziekenhuizen Leuven
Kapucijnenvoer 33
Phone : +(32) 16 33 29 77 B-3000 Leuven, Belgium
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