Date: Sat, 2 May 2009 14:11:23 -0500 From: Alan Cox <alan.l.cox@gmail.com> To: Freddie Cash <fjwcash@gmail.com> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: current zfs tuning in RELENG_7 (AMD64) suggestions ? Message-ID: <ca3526250905021211h4f9139a4xe1b0e429b465c402@mail.gmail.com> In-Reply-To: <b269bc570905011628x61105871t5fb0cdbad310ac1c@mail.gmail.com> References: <E1LzzjJ-0002eV-5A@dilbert.ticketswitch.com> <32A0BDD9-ACF8-43F4-8D2C-0FC151F1D7CB@cryptomonkeys.org> <b269bc570905011628x61105871t5fb0cdbad310ac1c@mail.gmail.com>
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On Fri, May 1, 2009 at 6:28 PM, Freddie Cash <fjwcash@gmail.com> wrote: > 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="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 the current max) This information is outdated.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. Regards, Alan
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