Luke Lonergan wrote:

On 11/18/05 8:13 AM, "Alan Stange" <[EMAIL PROTECTED]> 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
    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,


-- Alan

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