current zfs tuning in RELENG_7 (AMD64) suggestions ?

[Freddie Cash]

On Sat, May 2, 2009 at 12:11 PM, Alan Cox <alan.l.cox at gmail.com> wrote:
> On Fri, May 1, 2009 at 6:28 PM, Freddie Cash <fjwcash at gmail.com> wrote:
>> On Fri, May 1, 2009 at 4:12 PM, Louis Kowolowski
>> <louisk at cryptomonkeys.org> wrote:
>> > On May 1, 2009, at 1:53 PM, Pete French wrote:
>> >> ...
>> >> The tuning isn't there to improve performance, it's there to prevent
>> >> the box going titus due to a panic when the ARC gets too big, and
>> >> you are missing the mian one, which is to limit the size of the ARC.
>> >> On recent versions of BSD (and you are running 7.2, so thats fine) then
>> >> the defaults for kmem size are fine, but you still need something like
>> >> this:
>> >>
>> >> vfs.zfs.arc_max="256M"
>> >>
>> >> In there to stop the ARC growing. thats the only tuning I have on
>> >> my 4 gig machine, which takes a steady stream of data and is used
>> >> for taking backup snapshots. ZFS is excellent, and for me is perfectly
>> >> stable, to the point where I am starting to roll it out to production
>> >> machines, with the above tuning.
>> >>
>> > I agree, although I'm using 384 instead of 256.  My systems have been
>> > running in production for almost a year now w/o any ZFS issues.
>>
>> The exact value to use will depend on the system.  Particularly on the
>> amount of RAM in the system, and what kmem_max is set to.  A
>> "rule-of-thumb" we've been using is:
>>   kmem_max should be half of the amount of RAM (or 1.5 GB as that's
>> the current max)
>
> This information is outdated.  The current max in RELENG_7 for amd64 is
> ~3.75GB.

Nice!  Good to hear.  Thanks for the correction.  Looking forward to
testing this with 7.2.

-- 
Freddie Cash
fjwcash at gmail.com