Observations from a ZFS reorganization on 12-STABLE

[Rainer Duffner]

> Am 17.03.2019 um 15:58 schrieb Karl Denninger <karl at denninger.net>:
> 
> I've long argued that the VM system's interaction with ZFS' arc cache
> and UMA has serious, even severe issues.  12.x appeared to have
> addressed some of them, and as such I've yet to roll forward any part of
> the patch series that is found here [
> https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594 <https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=187594> ] or the
> Phabricator version referenced in the bug thread (which is more-complex
> and attempts to dig at the root of the issue more effectively,
> particularly when UMA is involved as it usually is.)
> 
> Yesterday I decided to perform a fairly significant reorganization of
> the ZFS pools on one of my personal machines, including the root pool
> which was on mirrored SSDs, changing to a Raidz2 (also on SSDs.)  This
> of course required booting single-user from a 12-Stable memstick.



Interesting.

The patches published before Christmas 2018 solved all of the problems I had (shared by many others, probably also visible on the FreeBSD project’s own infrastructure) with 11.2 and 12.0

I run a decently sized syslog-server and the 25MB/s stream of syslog-data was killing 11.2 almost instantly.

I have a few 11.2 systems that I haven’t patched yet - but they have north of 128GB of RAM and ARC had been configured down to 70% long before that - so I never saw the issue there.