From owner-freebsd-stable  Fri Sep 28 15:12: 9 2001
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Date: Fri, 28 Sep 2001 15:12:04 -0700
From: Kris Kennaway <kris@obsecurity.org>
To: Nate Williams <nate@yogotech.com>
Cc: Kris Kennaway <kris@obsecurity.org>,
	Alessandro de Manzano <ale@unixmania.net>,
	Sean Chittenden <sean@chittenden.org>, stable@FreeBSD.ORG
Subject: Re: dirpref gives massive performance boost
Message-ID: <20010928151204.A16750@xor.obsecurity.org>
References: <20010928141246.A15515@xor.obsecurity.org> <20010928232009.A29187@libero.sunshine.ale> <20010928142611.A15946@xor.obsecurity.org> <20010928143016.H29974@rand.tgd.net> <20010928233800.B29391@libero.sunshine.ale> <20010928144146.A16221@xor.obsecurity.org> <15284.62680.507872.259266@nomad.yogotech.com>
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In-Reply-To: <15284.62680.507872.259266@nomad.yogotech.com>; from nate@yogotech.com on Fri, Sep 28, 2001 at 04:08:24PM -0600
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On Fri, Sep 28, 2001 at 04:08:24PM -0600, Nate Williams wrote:
> > > > > Well, you need to wipe the disk so that when you restore it can l=
ay
> > > > > things out optimally from the start.
> > > >=20
> > > > But turning on soft-updates should be sufficient to get these perfo=
rmance=20
> > > > boosts from this point on, correct?  -sc
> > >=20
> > > AFAIK SU is not related to the physical layout of data on disk, this =
is
> > > the work of UFS_DIRHASH.
> >=20
> > No, that's something different.
> >=20
> > # Directory hashing improves the speed of operations on very large
> > # directories at the expense of some memory.
> > # Warning: this is experimental code!
> > options         UFS_DIRHASH
> >=20
> > The changes to dirpref are an improved on-disk layout policy for
> > directories (and files?)  It's enabled by default because there's no
> > downside.
>=20
> Again, I thought DIRHASH was an in-core data structure that helps with
> cache lookups for large directories, and had no effect on the on-disk
> layout.  (Hence the reason why it is 'safe' to use in -stable.)

Yes, like I said in the text you quoted, they *are* different things.

Kris

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