From owner-freebsd-stable@FreeBSD.ORG Thu Feb 24 22:49:56 2011 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D509B106566C for ; Thu, 24 Feb 2011 22:49:56 +0000 (UTC) (envelope-from jdc@koitsu.dyndns.org) Received: from qmta10.westchester.pa.mail.comcast.net (qmta10.westchester.pa.mail.comcast.net [76.96.62.17]) by mx1.freebsd.org (Postfix) with ESMTP id 4630B8FC0C for ; Thu, 24 Feb 2011 22:49:56 +0000 (UTC) Received: from omta20.westchester.pa.mail.comcast.net ([76.96.62.71]) by qmta10.westchester.pa.mail.comcast.net with comcast id BxhS1g0061YDfWL5Aypwzz; Thu, 24 Feb 2011 22:49:56 +0000 Received: from koitsu.dyndns.org ([98.248.33.18]) by omta20.westchester.pa.mail.comcast.net with comcast id Bypu1g00z0PUQVN3gypvr1; Thu, 24 Feb 2011 22:49:56 +0000 Received: by icarus.home.lan (Postfix, from userid 1000) id 0F8A59B422; Thu, 24 Feb 2011 14:49:53 -0800 (PST) Date: Thu, 24 Feb 2011 14:49:53 -0800 From: Jeremy Chadwick To: Christer Solskogen Message-ID: <20110224224952.GA17579@icarus.home.lan> References: <4D660909.6090202@my.gd> <20110224075517.GA18146@icarus.home.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: "freebsd-stable@freebsd.org" Subject: Re: ZFS - abysmal performance with samba since upgrade to 8.2-RELEASE X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 24 Feb 2011 22:49:56 -0000 On Thu, Feb 24, 2011 at 07:23:54PM +0100, Christer Solskogen wrote: > On Thu, Feb 24, 2011 at 8:55 AM, Jeremy Chadwick > 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 |