Обсуждение: 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

Alan,

On 11/18/05 9:31 AM, "Alan Stange" <stange@rentec.com> wrote:

> 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.

Cool - thanks for the results.  Is that % of one CPU, or of 2?  Was the
system otherwise 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.

Are you happy with 130MB/s?  How much did you pay for that?  Is it more than
$2,000, or double my 2003 PC?

> 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,

Cool.  Would that be Sandia?

We routinely sustain 2,000 MB/s from disk on 16x 2003 era machines on
complex queries.

- Luke