ZFS ARC being limited below what is defined in /boot/loader.conf

[Artem Belevich]

Check your vm.kmem_size. Default setting is way too low. Set it to at
least double of desired arc size.

--Artem



On Fri, Feb 12, 2010 at 10:31 AM, Steve Polyack <korvus at comcast.net> wrote:
> Has anyone had an issue with the ZFS ARC max being limited below what has
> been defined in /boot/loader.conf?  I just upgraded the RAM in a
> ZFS-equipped system and attempted to devote 4GB to the ARC cache by placing
> the following in loader.conf:
>  vfs.zfs.arc_max="4096M"
>
> However, after rebooting, querying the sysctl gives me this:
> $ sysctl vfs.zfs.arc_max
> vfs.zfs.arc_max: 1726489600
>
> or about 1.7GB, an odd number that I can't find any references to.  For
> reference, I'm running 8-STABLE (as of Jan 19th) on an amd64 system with 8GB
> of RAM.  The system was previously very stable with 4GB of RAM and a 512MB
> arc_max.  I have not modified vm.kmem_size_max (defaults to ~330GB on amd64)
> or any other ZFS tunables.  I'd also like to avoid syncing up to the current
> 8-STABLE if at all possible.
>
> Thanks,
> Steve Polyack
>
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