From owner-freebsd-fs@FreeBSD.ORG Thu Oct 13 04:17:41 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 360D21065674 for ; Thu, 13 Oct 2011 04:17:41 +0000 (UTC) (envelope-from freebsd@penx.com) Received: from Elmer.dco.penx.com (elmer.dco.penx.com [174.46.214.165]) by mx1.freebsd.org (Postfix) with ESMTP id E844B8FC15 for ; Thu, 13 Oct 2011 04:17:40 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by Elmer.dco.penx.com (8.14.5/8.14.4) with ESMTP id p9D4HbqD028476 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 12 Oct 2011 22:17:39 -0600 (MDT) (envelope-from freebsd@penx.com) Date: Wed, 12 Oct 2011 22:17:37 -0600 (MDT) From: Dennis Glatting X-X-Sender: dennisg@Elmer.dco.penx.com To: Steven Hartland Message-ID: User-Agent: Alpine 2.00 (BSF 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII 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: Thu, 13 Oct 2011 04:17:41 -0000 On Wed, 2011-10-12 at 08:59 +0100, Steven Hartland wrote: ----- Original Message ----- > From: "Dennis Glatting" > > > >I would appreciate someone knowledgeable in ZFS point me in the right > > direction. > > > > I have several ZFS arrays, some using gzip for compression. The > > compressed arrays hold very large text documents (10MB->20TB) > > and are highly compressible. Reading the files from a compressed > > data sets is fast with little load. However, writing to the > > compressed data sets incurs substantial load on the order of a > > load average from 12 to 20. > > > > My questions are: > > > > 1) Why such a heavy load on writing? > > 2) What kind of limiters can I put into effect to reduce load > > without impacting compressibilty? For example, is there some > > variable to controls the number of parallel compression > > operations? > > > > I have a number of different systems. Memory is 24GB on each of the two > > large data systems, SSD (Revo) for cache, and a SATA II ZIL. One system is > > a 6 core i7 @ 3.33 GHz and the other 4 core ii7 @ 2.93 GHz. The arrays are > > RAIDz using cheap 2TB disks. > > Have you tried using the alternative compression algorithms > e.g. lzjb or gzip-[1-5] the default gzip = gzip-6 > I have tried lzjb and I am unimpressed. I have not tried different levels of gzip on ZFS but I have tried it on documents with results I expected. As I mentioned, I have a lot of data. Two files were 26GB uncompressed but I had to kill those data sets because I ran out of room (I have reorganized my arrays since then). My ZFS compression ratio is 4.93x and I would require more storage at different gzip levels or ljzb. An option is not too compress with ZFS rather directly with gzip however I would still need lots of temporary storage for manipulation, which is what I am doing now (e.g., sort). Processing with zcat isn't always a good solution because some applications want files, but you have to do what you have to do. > Regards > Steve > > ================================================ > This e.mail is private and confidential between Multiplay (UK) Ltd. and the person or entity to whom it is addressed. In the event of misdirection, the recipient is prohibited from using, copying, printing or otherwise disseminating it or any information contained in it. > > In the event of misdirection, illegible or incomplete transmission please telephone +44 845 868 1337 > or return the E.mail to postmaster@multiplay.co.uk. > > _______________________________________________ > freebsd-fs@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-fs > To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > -- Dennis Glatting