Re: HEADS UP - HAMMER work

[Michael Neumann <mneumann@xxxxxxxx>]

Dennis Melentyev schrieb:
> 2008/11/15 Michael Neumann <mneumann@ntecs.de>:
> > Dennis Melentyev schrieb:
> ...
> > > Sysctl/some-other-tunable with some kind of mask would be great for
> > > fine-tuning (and just useless for the 90% of users).
> > >
> > > like:
> > > sysctl.hammer.dirhash.hashmask.prefix=1 (Starting at first filename
> > > byte, 3 bytes fixed length)
> > > sysctl.hammer.dirhash.hashmask.suffix=-1 (Starting last byte, 2 bytes
> > > length)
> > Hm, but the hash is stored on-disk within each b-tree node, so changing the
> > hash-function becomes pretty dangerous!
>
> That could be done via an option upon PFS creation, changed with
> "hammer" utility parameter, whatever else way. As I wrote:
> "sysctl/some-other-tunable".

Ah okay. A per-PFS setting would make sense to me.

> Anyway, for me, it is fine tuning issue. Quite rare and very special
> one. I hardly see any need in such thing for 99% of installations, but
> there sure are cases when it is a huge plus.

That's why I'd prefer to just have one good heuristic which is in any 
way better than what UFS provides.

Regards,

  Michael