Re: random i/o speedup weirdness

From: Jens Axboe <>
Date: Mon, 21 May 2007 13:28:58 +0200

On Mon, May 14 2007, Jens Axboe wrote:
> On Mon, May 14 2007, wrote:
> > > Probably because fio gives up finding new free random blocks and then it
> > > sort-of becomes a bit more sequential. Can you check if adding
> > > 'norandommap' to the options makes that effect go away?
> >
> > just finished testing -- yes, 'norandommap' makes the effect go away
> > while producing consistent results with the original test.
> Great, I think I'll try making that the default option then, or at least
> fixup the randommap behaviour. Using a random map is mainly beneficial
> for write verifying.

Instead I opted to try and fix the behaviour. It likely wont be perfect,
but some testing here shows that the IO at the end differs no more than
the noise during the entire run.

So can I ask you to repeat the test with a current version of fio? I'd
suggest just grabbing:

or doing a git pull to update, whichever is your preference.

Jens Axboe
Received on Mon May 21 2007 - 13:28:58 CEST

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