Subject: Re: ffs fragmentation
To: Jaromir Dolecek <>
From: Eduardo E. Horvath <>
List: tech-kern
Date: 05/14/1999 10:06:41
On Fri, 14 May 1999, Jaromir Dolecek wrote:

> Guenther Grau wrote:
> > Might make sense? I don't know. How large is the fragmentation
> > using ffs? I don't think it's usually worth running a daemon
> > cleaning it up. Might make more sense for different filesystems, though.
> For me - 3% after about a half a year; the NetBSD portion
> is nearly full last 4 months and I run out of all space several times
> (I mean all as all - even the 10% spare root-only space). The
> fragmentation seems to stay constant now.
> My other computer has about 2% fragmentation after about three
> years -- this one has plenty of free room though.
> Both are desktop computers only though.

The ffs design is such that it does not suffer from fragmentation, or
looking at it another way, forces a low level of fragmentation on
everything.  So running a defrag utility is redundant, useless, and
possibly dangerous since you could potentially lose data.

This also means that you can't really store swap blocks near the
associated file blocks since the file blocks are scattered in large
clumps across the disk.  

Ideally if you were going to do this you would want to allocate the swap
blocks as if they were part of a normal file to mimize any performance
degradation.  But if you did, there would be no real benefit over using a
standard swap file.

Eduardo Horvath
	"I need to find a pithy new quote." -- me