Date: Wed, 9 Sep 2009 08:07:37 -0500 From: Peter Steele <psteele@maxiscale.com> To: 'Daniel Bye' <freebsd-questions@slightlystrange.org>, "'freebsd-questions@freebsd.org'" <freebsd-questions@freebsd.org> Subject: RE: Using mdconfig for swap space Message-ID: <7B9397B189EB6E46A5EE7B4C8A4BB7CB3037EC0A@MBX03.exg5.exghost.com> In-Reply-To: <20090909105707.GA27941@torus.slightlystrange.org> References: <7B9397B189EB6E46A5EE7B4C8A4BB7CB3037EBB7@MBX03.exg5.exghost.com> <20090908235259.GB19173@gizmo.acns.msu.edu> <20090909105707.GA27941@torus.slightlystrange.org>
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Thanks for the responses. The reason I'm looking at doing this is that we h=
ave increased memory on our platform from 4GB to 8GB and therefore have to =
increase swap space from 8GB to 16GB. We have enough space in our /var part=
ition that we could add a swap file there and not have to touch the existin=
g partition layout. I like the simplicity of the swap file approach, but we=
have an application that is very sensitive to I/O performance and I'm a li=
ttle wary what this could mean. QA I know would have a field day in trying =
to pound the system with all sorts of stress tests. I think a dedicated swa=
p partition is probably a safer option.
Peter
-----Original Message-----
From: owner-freebsd-questions@freebsd.org [mailto:owner-freebsd-questions@f=
reebsd.org] On Behalf Of Daniel Bye
Sent: Wednesday, September 09, 2009 3:57 AM
To: 'freebsd-questions@freebsd.org'
Subject: Re: Using mdconfig for swap space
On Tue, Sep 08, 2009 at 07:52:59PM -0400, Jerry McAllister wrote:
> On Tue, Sep 08, 2009 at 04:51:20PM -0500, Peter Steele wrote:
>=20
> > Are there any advantages to using mdconfig and creating a virtual disk =
for swap space as opposed to having a designated swap partition? For exampl=
e, I could do something like this:
>=20
> Unless I am missing something basic here, it seems like a bad idea to=20
> me - to carve out and use up some memory to use as extra storage for=20
> processes that need more memory that you have taken away to give to swap.
> That is self defeating.
>=20
> In addition, one use of swap is to write dumps to if there is a crash.=20
> If you put it in memory, it is gone when you reboot.
He's talking about using a swap file, rather than a dedicated partition on =
the disk, not in RAM! Although it is slightly slower, as Chuck has already =
pointed out, it might, in certain circumstances, be a somewhat more conveni=
ent solution than repartitioning/reinstalling the whole system.
And as RW has said, the facility already exists and can be enabled with a c=
ouple of knobs in /etc/rc.conf.
Dan
--
Daniel Bye
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