Unix administration - Bonnie Benchmark puzzle

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Author Bonnie Benchmark puzzle
Gary Barnette

2004-01-23, 4:53 pm

For those that may not know, Bonnie is a great little disk benchmark tool
available on the net. Show Kbytes/second and %CPU time for different write,
read, and seek tests.

The setup:
I haven't run Bonnie for awhile on a box (HP RP8400) and then I run it
several times in a row. The first time it is run all of the write tests are
from 2-4 times as slow (depending on which test) as all the other subsequent
tests. The read tests are all very close, including the first time it is
run.

I'm sure it has something to do with buffer cache but I don't understand
what.

Anyone have an explanation? I would be glad to provide any other needed
information.

The reason I'm asking is that on another box of the same type, the write
test never does get better, even after the first running of Bonnie and this
box has a bad write performance problem. I am trying desperately to fix it.

Many Thanks,
Gary
gbarnette@adelphia.net


Mangled&Munged

2004-01-23, 4:54 pm

Hmmm.... I would have used Iozone. It can show
you the performance when the aggregate data set
fits in the buffer cache, and when it does not.

See: http://www.iozone.org



"Gary Barnette" <gbarnette@adelphia.net> wrote in message
news:%ODsb.407$_i1.240424@news2.news.adelphia.net...
quote:

> For those that may not know, Bonnie is a great little disk benchmark tool
> available on the net. Show Kbytes/second and %CPU time for different


write,
quote:

> read, and seek tests.
>
> The setup:
> I haven't run Bonnie for awhile on a box (HP RP8400) and then I run it
> several times in a row. The first time it is run all of the write tests


are
quote:

> from 2-4 times as slow (depending on which test) as all the other


subsequent
quote:

> tests. The read tests are all very close, including the first time it is
> run.
>
> I'm sure it has something to do with buffer cache but I don't understand
> what.
>
> Anyone have an explanation? I would be glad to provide any other needed
> information.
>
> The reason I'm asking is that on another box of the same type, the write
> test never does get better, even after the first running of Bonnie and


this
quote:

> box has a bad write performance problem. I am trying desperately to fix


it.
quote:

>
> Many Thanks,
> Gary
> gbarnette@adelphia.net
>
>




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