[Bulk] Re: How much swap space for a 32 GB RAM system?

Lowell Gilbert freebsd-questions-local at be-well.ilk.org
Tue Jul 22 19:29:45 UTC 2014

Ralf Mardorf <ralf.mardorf at rocketmail.com> writes:

> On Tue, 2014-07-22 at 13:35 -0400, Michael Powell wrote:
>> Since I don't use such things (me sysadmin - not a coder) I'm not as 
>> knowledgeable, but I seem to recall that a crash dump needs a swap
>> that is as large as physical memory.
> "My 48GB swap file system isn't fully recognized.
> Q. What is the max amount of swap a system can use?
> A. Are you sure you want/need that much swap anyway? The old-school 2-4x
> RAM doesn't really apply, though you may want a bit more than 1x
> physical RAM if you are capturing a crash dump, and some systems have
>>32GB RAM now. Swap can be limited by kern.maxswzone which controls the
> size of metadata use to track swap (8.X default is 64MB allowing ~15GB
> of swap). Note other changes are required to have >8x physical RAM for
> swap." - https://commons.lbl.gov/display/~jwelcher@lbl.gov/FreeBSD
> +Random+FAQ

That's a little out of date, because crash dumps now default to a
minidump and take much less space. You're unlikely to want a full dump
and can always add a new disk for the purpose if you ever do.

> Interesting thread, since there isn't an answer for Linux and I plan to
> use a new FreeBSD install in the close future too.

Fair enough. There's always advice to be found, but "how much swap" in a
vastly less interesting or consequential question than it used to be.

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