Re: Hardware/OS recommendations for large databases (

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