Using mdconfig for swap space
freebsd-questions-local at be-well.ilk.org
Wed Sep 9 15:23:16 UTC 2009
Jerry McAllister <jerrymc at 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
More information about the freebsd-questions