From owner-freebsd-fs@FreeBSD.ORG Wed Oct 12 19:39:42 2011 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 D8324106566B for ; Wed, 12 Oct 2011 19:39:42 +0000 (UTC) (envelope-from bfriesen@simple.dallas.tx.us) Received: from blade.simplesystems.org (blade.simplesystems.org [65.66.246.74]) by mx1.freebsd.org (Postfix) with ESMTP id 6FC848FC12 for ; Wed, 12 Oct 2011 19:39:41 +0000 (UTC) Received: from freddy.simplesystems.org (freddy.simplesystems.org [65.66.246.65]) by blade.simplesystems.org (8.14.4+Sun/8.14.4) with ESMTP id p9CJdeKg005710; Wed, 12 Oct 2011 14:39:40 -0500 (CDT) Date: Wed, 12 Oct 2011 14:39:40 -0500 (CDT) From: Bob Friesenhahn X-X-Sender: bfriesen@freddy.simplesystems.org To: Jeremy Chadwick In-Reply-To: <20111012165126.GA26562@icarus.home.lan> Message-ID: References: <20111012165126.GA26562@icarus.home.lan> User-Agent: Alpine 2.01 (GSO 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.2 (blade.simplesystems.org [65.66.246.90]); Wed, 12 Oct 2011 14:39:40 -0500 (CDT) Cc: freebsd-fs@freebsd.org Subject: Re: ZFS/compression/performance 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: Wed, 12 Oct 2011 19:39:43 -0000 On Wed, 12 Oct 2011, Jeremy Chadwick wrote: > > That might be the case on OpenSolaris but the performance hit on > FreeBSD RELENG_8 is very high -- enough that enabling compression (using > the defaults) causes stalls when I/O occurs (easily noticeable across > SSH; characters are delayed/stalled (not buffered)), etc.. Solaris solved the problem by putting the zfs writer threads into a special scheduling class so that they are usually lower priority than normal processing. Before this change, a desktop system would become almost unusable (intermittent loss of keyboard/mouse) while writing lots of data with compression enabled. Some NFS servers encountered severe enough issues that NFS clients reported NFS timeouts. > Another point: I haven't tinkered with compression on our Solaris 10 > machines at work so I don't know if it performs better, equal, or worse > than FreeBSD or OpenSolaris. >From what you describe, Solaris must be doing much better in this regard than FreeBSD. Solaris is not necessarily faster but there is now little impact on interactive tasks. Bob -- Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/