Date: Wed, 09 Sep 2009 11:23:14 -0400 From: Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> To: Jerry McAllister <jerrymc@msu.edu> Cc: "'freebsd-questions@freebsd.org'" <freebsd-questions@freebsd.org> Subject: Re: Using mdconfig for swap space Message-ID: <44tyzcuopp.fsf@be-well.ilk.org> In-Reply-To: <20090909145922.GB22253@gizmo.acns.msu.edu> (Jerry McAllister's message of "Wed, 9 Sep 2009 10:59:23 -0400") References: <7B9397B189EB6E46A5EE7B4C8A4BB7CB3037EBB7@MBX03.exg5.exghost.com> <20090908235259.GB19173@gizmo.acns.msu.edu> <20090909105707.GA27941@torus.slightlystrange.org> <20090909145922.GB22253@gizmo.acns.msu.edu>
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Jerry McAllister <jerrymc@msu.edu> writes: > On Wed, Sep 09, 2009 at 11:57:07AM +0100, Daniel Bye wrote: > >> 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: >> > >> > > Are there any advantages to using mdconfig and creating a virtual disk for swap space as opposed to having a designated swap partition? For example, I could do something like this: >> > >> > Unless I am missing something basic here, it seems like a bad idea to >> > me - to carve out and use up some memory to use as extra storage for >> > processes that need more memory that you have taken away to give to swap. >> > That is self defeating. >> > >> > In addition, one use of swap is to write dumps to if there is a crash. >> > 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 >> convenient solution than repartitioning/reinstalling the whole system. >> >> And as RW has said, the facility already exists and can be enabled with a >> couple of knobs in /etc/rc.conf. > > I understand using a file and making it in to swapspace. I have used that > a couple of times when I needed to add some swap space temporarily. But > isn't the command he is trying to use (mdconfig) for creating a memory > filesystem - eg use a chunk of memory and make a file from it (then use it > for swap or whatever)? That is in RAM. Not necessarily. What he wants is the '-t vnode' option for mdconfig(8). -- Lowell Gilbert, embedded/networking software engineer, Boston area http://be-well.ilk.org/~lowell/
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