Luke Lonergan wrote:
> Alan,
>
> On 11/18/05 8:13 AM, "Alan Stange" <stange@rentec.com> wrote:
>
> I told you in my initial post that I was observing numbers in
> excess of
> what you claiming, but you seemed to think I didn't know how to
> measure
> an IO rate.
>
> Prove me wrong, post your data.
>
> I should note too that our system uses about 20% of a single cpu when
> performing a table scan at >100MB/s of IO. I think you claimed the
> system would be cpu bound at this low IO rate.
>
>
> See above.
Here's the output from one iteration of iostat -k 60 while the box is
doing a select count(1) on a 238GB table.
avg-cpu: %user %nice %sys %iowait %idle
0.99 0.00 17.97 32.40 48.64
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sdd 345.95 130732.53 0.00 7843952 0
We're reading 130MB/s for a full minute. About 20% of a single cpu was
being used. The remainder being idle.
We've done nothing fancy and achieved results you claim shouldn't be
possible. This is a system that was re-installed yesterday, no tuning
was done to the file systems, kernel or storage array.
What am I doing wrong?
9 years ago I co-designed a petabyte data store with a goal of 1GB/s IO
(for a DOE lab). And now I don't know what I'm doing,
Cheers,
-- Alan