From owner-freebsd-fs@FreeBSD.ORG Fri Dec 25 19:54:57 2009 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 8F0B9106568D for ; Fri, 25 Dec 2009 19:54:57 +0000 (UTC) (envelope-from james-freebsd-fs2@jrv.org) Received: from mail.jrv.org (rrcs-24-73-246-106.sw.biz.rr.com [24.73.246.106]) by mx1.freebsd.org (Postfix) with ESMTP id 541A58FC24 for ; Fri, 25 Dec 2009 19:54:56 +0000 (UTC) Received: from kremvax.housenet.jrv (kremvax.housenet.jrv [192.168.3.124]) by mail.jrv.org (8.14.3/8.14.3) with ESMTP id nBPJssiP098939; Fri, 25 Dec 2009 13:54:55 -0600 (CST) (envelope-from james-freebsd-fs2@jrv.org) Authentication-Results: mail.jrv.org; domainkeys=pass (testing) header.from=james-freebsd-fs2@jrv.org DomainKey-Signature: a=rsa-sha1; s=enigma; d=jrv.org; c=nofws; q=dns; h=message-id:date:from:user-agent:mime-version:to:cc:subject: references:in-reply-to:content-type:content-transfer-encoding; b=OJ0EeuZ1MrVd1KPWoEQ1SlaWACnYHvhm+i2CwapTzodm9jsPMlsAOfhvD5uHzPNJA waBL5MslXQvWJ/9HQXSokUNkLq1ynAWiiCYUgP1VmOLjQjJYc6UzIODY634SpQBExSV +CALWxcEzsGAQLJOfXTygvJxDTX4SRw1t+MWaNs= Message-ID: <4B35188E.7010602@jrv.org> Date: Fri, 25 Dec 2009 13:54:54 -0600 From: "James R. Van Artsdalen" User-Agent: Thunderbird 2.0.0.23 (Macintosh/20090812) MIME-Version: 1.0 To: Solon Lutz References: <568624531.20091215163420@pyro.de> <42952D86-6B4D-49A3-8E4F-7A1A53A954C2@spry.com> <957649379.20091216005253@pyro.de> <26F8D203-A923-47D3-9935-BE4BC6DA09B7@corp.spry.com> <1696529130.20091223212612@pyro.de> In-Reply-To: <1696529130.20091223212612@pyro.de> Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: freebsd-fs@freebsd.org Subject: Re: ZFS RaidZ2 with 24 drives? X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 25 Dec 2009 19:54:57 -0000 Solon Lutz wrote: > I opted for two 12-disc raidz2. > Reasons were: Space is more important than performance. > > But performance is very poor - have a look at the iostats Try a RAIDZ with fewer drives - maybe four drives - and see if performance is better. 12 drives in RAIDZ2 may result in a stripe that is just too big for the writes your tests do. > sometimes nothing really seems > to happen for up to ten seconds, or very little data gets written. Might this be a problem > of the amd64 system having only 4GB of RAM? Any tuneable sysctls? Enabling prefetch didn't help...: Any copy-on-write filesystem is going to greatly benefit from very aggressive write-deferral and combining. The cache probably isn't flushed unless it needs to be, or until the next transaction group commit. "10 seconds" is roughly the usual interval for ZFS commits. This is likely not a problem.