using mfs of size > 64Mb and system stability

[Barath S]

Where can I get details regarding the 'preload' backed
  ram disks ?. How is it different from "malloc" based
ram disks?  As per 'man mdconfig', there is no such
option available.

Could you kindly provide me more hints on this?

Thanks 
--- Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:   
> In message
> <20050110135747.GA44905 at xor.obsecurity.org>, Kris
> Kennaway writes:
> >
> >--HlL+5n6rz5pIUxbD
> >Content-Type: text/plain; charset=us-ascii
> >Content-Disposition: inline
> >Content-Transfer-Encoding: quoted-printable
> >
> >On Mon, Jan 10, 2005 at 11:11:44AM +0100,
> Poul-Henning Kamp wrote:
> >> In message
>
<20050110100840.29845.qmail at web30301.mail.mud.yahoo.com>,
> Bara=
> >th S w
> >> rites:
> >> >Initially, I didn't go for swap based fs as I
> felt
> >> >that  the memory occupied will be from the swap
> area.
> >> >As you are saying that the allocation will be
> from
> >> >buffer/cache, I will test swap-mfs.
> >>=20
> >> malloc backing should not be used for large
> disks.
> >>=20
> >> If you _truly_ want to have a large disk which is
> memory backed,
> >> you should consider using the "preload" backing
> as this will withdraw
> >> the memory entirely from the kernels use.
> >>=20
> >> In general, the benefit from using RAM disks is
> much smaller than
> >> most people realize.
> >
> >I've found that using a swap-backed disk
> substantially cuts back on
> >disk accesses for my purposes [...]
> 
> Swap-backing is very different from RAM disks in
> that things get
> pushed out of RAM if better use can be made of the
> pages.
> 
> With RAM disks (preload or malloc backing) you
> occupy valuable
> RAM pages with free diskblocks.
> 
> -- 
> Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> phk at FreeBSD.ORG         | TCP/IP since RFC 956
> FreeBSD committer       | BSD since 4.3-tahoe    
> Never attribute to malice what can adequately be
> explained by incompetence.
>  

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