From owner-freebsd-fs@FreeBSD.ORG Wed Jun 12 11:49:59 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 7759D7E2 for ; Wed, 12 Jun 2013 11:49:59 +0000 (UTC) (envelope-from jdc@koitsu.org) Received: from relay3-d.mail.gandi.net (relay3-d.mail.gandi.net [217.70.183.195]) by mx1.freebsd.org (Postfix) with ESMTP id 36A69148F for ; Wed, 12 Jun 2013 11:49:59 +0000 (UTC) Received: from mfilter21-d.gandi.net (mfilter21-d.gandi.net [217.70.178.149]) by relay3-d.mail.gandi.net (Postfix) with ESMTP id 7AC14A80FB; Wed, 12 Jun 2013 13:49:41 +0200 (CEST) X-Virus-Scanned: Debian amavisd-new at mfilter21-d.gandi.net Received: from relay3-d.mail.gandi.net ([217.70.183.195]) by mfilter21-d.gandi.net (mfilter21-d.gandi.net [10.0.15.180]) (amavisd-new, port 10024) with ESMTP id TugAw4oebJsM; Wed, 12 Jun 2013 13:49:39 +0200 (CEST) X-Originating-IP: 76.102.14.35 Received: from jdc.koitsu.org (c-76-102-14-35.hsd1.ca.comcast.net [76.102.14.35]) (Authenticated sender: jdc@koitsu.org) by relay3-d.mail.gandi.net (Postfix) with ESMTPSA id A8520A80C4; Wed, 12 Jun 2013 13:49:39 +0200 (CEST) Received: by icarus.home.lan (Postfix, from userid 1000) id D0B3C73A1C; Wed, 12 Jun 2013 04:49:37 -0700 (PDT) Date: Wed, 12 Jun 2013 04:49:37 -0700 From: Jeremy Chadwick To: Mark Felder Subject: Re: An order of magnitude higher IOPS needed with ZFS than UFS Message-ID: <20130612114937.GA13688@icarus.home.lan> References: <51B79023.5020109@fsn.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Cc: freebsd-fs@freebsd.org X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 12 Jun 2013 11:49:59 -0000 On Wed, Jun 12, 2013 at 06:40:32AM -0500, Mark Felder wrote: > On Tue, 11 Jun 2013 16:01:23 -0500, Attila Nagy wrote: > > >BTW, the file systems are 77-78% full according to df (so ZFS > >holds more, because UFS is -m 8). > > ZFS write performance can begin to drop pretty badly when you get > around 80% full. I've not seen any benchmarks showing an improvement > with a very fast and large ZIL or tons of memory, but I'd expect > that would help significantly. Just note that you're right at the > edge where performance gets impacted. Mark, do you have any references for this? I'd love to learn/read more about this engineering/design aspect (I won't say flaw, I'll just say aspect) to ZFS, as it's the first I've heard of it. The reason I ask: (respectfully, not judgementally) I'm worried you might be referring to something that has to do with SSDs and not ZFS, specifically SSD wear-levelling performing better with lots of free space (i.e. a small FTL map; TRIM helps with this immensely) -- where the performance hit tends to begin around the 70-80% mark. (I can talk more about that if asked, but want to make sure the two things aren't being mistaken for one another) -- | Jeremy Chadwick jdc@koitsu.org | | UNIX Systems Administrator http://jdc.koitsu.org/ | | Making life hard for others since 1977. PGP 4BD6C0CB |