Date: Sat, 23 Jan 2010 10:25:13 +0100 From: Alexander Leidinger <Alexander@Leidinger.net> To: jhell <jhell@DataIX.net> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org>, Artem Belevich <fbsdlist@src.cx> Subject: Re: Setting "zfs_arc_max" value in FreeBSD 8. Message-ID: <20100123102513.00001f67@unknown> In-Reply-To: <alpine.BSF.2.00.1001222123400.3696@pragry.qngnvk.ybpny> References: <7f14551c1001190119x46c6b04dx2362cd1252f0d81@mail.gmail.com> <hj3v0i$i2p$1@ger.gmane.org> <7f14551c1001190216w49814186n1ada2b721380502b@mail.gmail.com> <4B55C5A6.2020109@DataIX.net> <20100120111433.25801pnmhrxnirok@webmail.leidinger.net> <ed91d4a81001220847v15e26830la2d51479c3d104e1@mail.gmail.com> <alpine.BSF.2.00.1001222123400.3696@pragry.qngnvk.ybpny>
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On Fri, 22 Jan 2010 21:39:48 -0500 jhell <jhell@DataIX.net> wrote: > > On Fri, 22 Jan 2010 11:47, fbsdlist@ wrote: > >>> Anyone know if it is adjustable on a system with 1024MB of ram ? > >>> Is this just being auto calculated by some other value ? > > > > You may want to make sure that vm.kmem_size is set to a value much > > larger than vfs.zfs.arc_max. Default value may be too small to allow > > such a large ARC. > > > > On a side note, I'm not sure that ZFS is a good match for system > > with only 1G of RAM. By trial and error on my box with 8G or memory > > I've figured out that I need to set arc_max ~1G below physical > > memory size to avoid lockups under load. YMMV. > > > > ZFS on this box with 1G has been quite enjoyable actually. With the > settings I have posted I have not had any lockup on stable/7 and no > sudden freezes or waits for transfers. So this entirely thus far has > been a godsend. I had even put this thing through some of the > tortures that others have posted to the list and not come up with the > same results but better. There is obviously a lot of variables in > this between hardware and configurations used so the results are > minimal in comparison. With ZFS in place on this machine it performs > a little bit under specs for the hardware but I wouldn't expect > anything less for such a file-system. You may want to switch to fletcher4 checksums. This is the default in Solaris and 8.0 now. I didn't merge this change to 7-stable as I didn't took the time to analyze if the change for the default has some unwanted implications for existig pools. I have a 9-current box with 1GB RAM and ZFS which shows the slow-down after some hours of running (and doing things) too. It would be good to make a list of OS versions and if there are slowdowns or not (anyone with time out there to have a look at the mails and get this info out of the mails / people?). Maybe it is related to changes not in ZFS... Bye, Alexander.
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