Date: Fri, 1 May 2009 16:28:40 -0700 From: Freddie Cash <fjwcash@gmail.com> To: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: current zfs tuning in RELENG_7 (AMD64) suggestions ? Message-ID: <b269bc570905011628x61105871t5fb0cdbad310ac1c@mail.gmail.com> In-Reply-To: <32A0BDD9-ACF8-43F4-8D2C-0FC151F1D7CB@cryptomonkeys.org> References: <E1LzzjJ-0002eV-5A@dilbert.ticketswitch.com> <32A0BDD9-ACF8-43F4-8D2C-0FC151F1D7CB@cryptomonkeys.org>
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On Fri, May 1, 2009 at 4:12 PM, Louis Kowolowski <louisk@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=3D"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. =C2=A0My systems have bee= n > 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) arc_max should be half of kmem_max Using those, we've been able to run our ZFS boxes without any kmem panics, even when doing rsync backups for 102 remote servers every night to a single box. Finding those values was fun. :( --=20 Freddie Cash fjwcash@gmail.com
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