Date: Wed, 9 Sep 2009 11:54:14 -0400 From: Jerry McAllister <jerrymc@msu.edu> To: "'freebsd-questions@freebsd.org'" <freebsd-questions@freebsd.org> Cc: Jerry McAllister <jerrymc@msu.edu> Subject: Re: Using mdconfig for swap space Message-ID: <20090909155414.GA22575@gizmo.acns.msu.edu> In-Reply-To: <44tyzcuopp.fsf@be-well.ilk.org> References: <7B9397B189EB6E46A5EE7B4C8A4BB7CB3037EBB7@MBX03.exg5.exghost.com> <20090908235259.GB19173@gizmo.acns.msu.edu> <20090909105707.GA27941@torus.slightlystrange.org> <20090909145922.GB22253@gizmo.acns.msu.edu> <44tyzcuopp.fsf@be-well.ilk.org>
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On Wed, Sep 09, 2009 at 11:23:14AM -0400, Lowell Gilbert wrote: > 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). Hmmm. Haven't dealt with that before. Still seems like either a regular file or a dedicated partition would be best. ////jerry > > -- > Lowell Gilbert, embedded/networking software engineer, Boston area > http://be-well.ilk.org/~lowell/
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