FreeBSD using swap even though there's a lot of free memory

Michael Sierchio kudzu at
Fri Oct 16 18:36:23 UTC 2020

On Thu, Oct 15, 2020 at 7:24 AM Twingly Customer Support <team at>

> Hi,
> We have a server running FreeBSD 12.1-RELEASE-p10. We currently have a
> problem where FreeBSD starting to swap when running ZFS scrub, even though
> we have ~70G of free memory.

tl;dr – this is normal, nothing to see, move along.

It's not "swapping" – it's paging pre-emptively.  If you're used to Linux,
you might think "swap bad"  ;-)   There is a lot of history to VM
management in BSD.  This might be an easy place to start:


"Well," Brahmā said, "even after ten thousand explanations, a fool is no
wiser, but an intelligent person requires only two thousand five hundred."

- The Mahābhārata

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