Some ideas for FreeBSD

Heiko Wundram (Beenic) wundram at
Thu Feb 7 07:36:28 UTC 2008

Am Donnerstag, 7. Februar 2008 08:26:07 schrieb Dominic Fandrey:
> Heiko Wundram (Beenic) wrote:
> > Am Donnerstag, 7. Februar 2008 07:32:16 schrieb Jason C. Wells:
> >> Norberto Meijome wrote:
> >>> But I agree with you really want to use swap files?
> >>
> >> One could mount an md filesystem and then use that as swap.  That way
> >> you wouldn't need to use any disc space.  As a plus, the performance
> >> would be way better than disc.
> >
> > Ahem, sorry, that's just plain stupid. Either the md system is backed up
> > by RAM (in which case you don't need the swap anyway; why'd you want to
> > access RAM by putting it in a swap on an md in RAM?), or it's backed up
> > by swap, in which case you have a chicken and egg problem.
> Or it's backed by a file (-t vnode, which is implicated by -f). I have used
> files for swap, just to see weather it works, others have done it because
> they had to.

True, sorry I forgot to mention that, but swapping to a file (based on a 
standard disk) won't get you any speed-ups relative to a (dedicated) 
swap-partition on a disk either, and that's (if I understood the original 
poster properly) what was suggested.

I can understand the need for swap files (esp. in some environments where 
there's no easy way to just add physical memory or disk space for a task 
requiring huge amounts of it), but generally they offer no speed up at all to 
a dedicated swap (or memory in itself).

Heiko Wundram
Product & Application Development

More information about the freebsd-questions mailing list