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Re: Sharded FSFS repositories

From: Ph. Marek <philipp.marek_at_bmlv.gv.at>
Date: 2007-03-20 15:37:57 CET

On Tuesday 20 March 2007 15:26, John Peacock wrote:
> Malcolm Rowe wrote:
> > My results:
> > - With one exception, sharding is always more expensive than not
> > sharding (because it adds an extra directory lookup). The difference
> > is negligible, however, because we're still talking about microseconds
> > per lookup.
> Thank you for taking the time to benchmark something, rather than
> relying on Magic Numbers (something I'm severely allergic to). ;-)
Yes, thank you very much.

Regarding your numbers - I think that linux might be a bad candidate, because
(as you said) it makes no difference as long as everything is cached.
I don't believe that the loopback mount makes *any* difference - the dentry
cache is the same.

Perhaps on a loaded system sharding would help, because a lot of dentries
could be evicted - on a single directory that could be much harder.

> > - We'll create shards of 1000 entries each. Anyone who has a repository
> > that's larger than a million revisions will likely be running on a
> > decent filesystem. Even if they aren't, we will still be much better
> > than we were before.
>
> I concur that this is a reasonable course. Malcolm++
+1 to both of you ;-)

Malcolm, thank you!

Regards,

Phil

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Received on Tue Mar 20 15:38:19 2007

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