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Re: Sharded FSFS repositories

From: Kevin Greiner <greinerk_at_gmail.com>
Date: 2007-03-22 18:09:08 CET

On 3/22/07, Ph. Marek <philipp.marek@bmlv.gv.at> wrote:

> I don't really know VBscript, but there are some things I notice:

My goal was to recreate what Malcolm had done based solely on his
description above. But some of your ideas were interesting although they
don't appear match what Malcolm has done.

- You open the file that you just created *and still have opened*.
> Maybe the lookups should be done in a second loop and/or another script.

- IIRC Win32 still uses timers (with HZ=150?), so you'll get time readings
> only with 7ms granularity.
> So it might be better to do 1000 lookups and measure their cumulative
> time,
> with different numbers of entries in the directories.
>
> > Does that change the conclusion at all?
> Could you please create the files, and try to access some (in *random*
> order)
> in another script?

OK, I did that. The summary: no change. NTFS appears to be just as fast for
this scenario as any other modern filesystem.

Across 1024 file opens in a directory of 2^20 files, an average time
(seconds) of 0.025 for not-sharded and 0.026 for sharded. See the attached
scripts and log files for the details. I ran the read script three times,
recording the 3rd iteration's time to minimize the impact of my slower
laptop.

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Received on Thu Mar 22 18:09:31 2007

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