Date: Thu, 24 Feb 2011 14:49:53 -0800 From: Jeremy Chadwick <freebsd@jdc.parodius.com> To: Christer Solskogen <christer.solskogen@gmail.com> Cc: "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: Re: ZFS - abysmal performance with samba since upgrade to 8.2-RELEASE Message-ID: <20110224224952.GA17579@icarus.home.lan> In-Reply-To: <AANLkTi=qM8Jym1SpVSoYKC%2B1mqjmuYudVhT5m%2BhXQgJ7@mail.gmail.com> References: <4D660909.6090202@my.gd> <20110224075517.GA18146@icarus.home.lan> <AANLkTi=qM8Jym1SpVSoYKC%2B1mqjmuYudVhT5m%2BhXQgJ7@mail.gmail.com>
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On Thu, Feb 24, 2011 at 07:23:54PM +0100, Christer Solskogen wrote: > On Thu, Feb 24, 2011 at 8:55 AM, Jeremy Chadwick > <freebsd@jdc.parodius.com> wrote: > > > > > # Set TXG write limit to a lower threshold. This helps "level out" > > # the throughput rate (see "zpool iostat"). A value of 256MB works well > > # for systems with 4GB of RAM, while 1GB works well for us w/ 8GB on > > # disks which have 64MB cache. > > vfs.zfs.txg.write_limit_override=1073741824 > > > > > > Sorry if you have said this before, but could you elaborate a bit > about this number? For instance, how much does the cache on the disk > has to say. > In my case: 3x1.5TB raidz with WD15EADS-00R6B0 which has 32MB cache > and 12GB memory. What would you recommend and why. There's no real way to provide an in-depth analysis of this number; that is to say, hard disk parameters (RPM, cache, and overall performance of the drive (highly dependent upon on-disk firmware)) ultimately dictates what's "best" for this number. I also imagine number of disks plays a role as well This is why I advocate not messing with it unless you want to try and "level out" throughput. The value itself is literally 1024*1024*1024 (1GB). Don't think this is some magic number; it's just what I came up with. You can search the FreeBSD lists for references to the variable itself and find other people advocating values like ~33MByte, etc.. All depends on how you want the system to behave. I don't particularly like watching the system behave like I described (you snipped that portion of my text), which is why I use this variable. -- | Jeremy Chadwick jdc@parodius.com | | Parodius Networking http://www.parodius.com/ | | UNIX Systems Administrator Mountain View, CA, USA | | Making life hard for others since 1977. PGP 4BD6C0CB |
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