Tuning ZFS ARC for 512GB Memory

Gezeala M. Bacuño II gezeala at gmail.com
Wed Mar 6 05:47:51 UTC 2013

Try to read through the email thread I have started and specifically posts
(replies) by alc:


I have followed his suggestions, and with the arc_max setting I used we
still have on average free RAM ~137GB.


On Tue, Mar 5, 2013 at 6:36 PM, Reed A. Cartwright <cartwright at asu.edu>wrote:

> I have a 512GB memory system that has a 480GB (or so) L2ARC, and a
> raidz2 storage pool.  No dedup or compression is enabled.  Although, I
> will enable compression in the future.
> By default vfs.zfs.arc_max is about 300GB and the L2ARC is hardly touched.
> I've seen a couple hints recently on the mailing lists that having too
> big of an ARC can be a performance hit because it takes a long time to
> inspect it when something needs to integrate over the entries.
> I've also had issues with running 9.1 on this machine due to zfs
> deadlocks or stalls and am currently "stuck" using 9.0 with no issue.
> So, I was wondering if shrinking the ARC would potentially help and
> what should I shrink it to?
> I am thinking about setting vfs.zfs.arc_max to 64GB.
> Does anyone have an opinion?
> --
> Reed A. Cartwright, PhD
> Assistant Professor of Genomics, Evolution, and Bioinformatics
> School of Life Sciences
> Center for Evolutionary Medicine and Informatics
> The Biodesign Institute
> Arizona State University
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