From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S966126AbXDGRKm (ORCPT ); Sat, 7 Apr 2007 13:10:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S966131AbXDGRKl (ORCPT ); Sat, 7 Apr 2007 13:10:41 -0400 Received: from h80ad275a.async.vt.edu ([128.173.39.90]:36611 "EHLO h80ad275a.async.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S966126AbXDGRKk (ORCPT ); Sat, 7 Apr 2007 13:10:40 -0400 X-Mailer: exmh version 2.7.2 01/07/2005 with nmh-1.2 To: Krzysztof Halasa Cc: johnrobertbanks@fastmail.fm, Jan Harkes , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: Reiser4. BEST FILESYSTEM EVER. In-Reply-To: Your message of "Sat, 07 Apr 2007 16:11:46 +0200." From: Valdis.Kletnieks@vt.edu References: <46157B5B.5000602@gmail.com> <1175817921.18400.1183285196@webmail.messagingengine.com> <461592FB.5060507@zytor.com> <1175819681.20754.1183287946@webmail.messagingengine.com> <461596DE.2020802@zytor.com> <1175823288.25662.1183293506@webmail.messagingengine.com> <4615C780.5040407@zytor.com> <1175833931.8916.1183307802@webmail.messagingengine.com> <20070406152119.GC4228@delft.aura.cs.cmu.edu> <1175914056.9653.1183426876@webmail.messagingengine.com> <20070407033049.GI4228@delft.aura.cs.cmu.edu> <1175925525.21154.1183436614@webmail.messagingengine.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1175965831_4736P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Sat, 07 Apr 2007 13:10:31 -0400 Message-ID: <13684.1175965831@turing-police.cc.vt.edu> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org --==_Exmh_1175965831_4736P Content-Type: text/plain; charset=us-ascii On Sat, 07 Apr 2007 16:11:46 +0200, Krzysztof Halasa said: > > Think about it,... read speeds that are some FOUR times the physical > > disk read rate,... impossible without the use of compression (or > > something similar). > > It's really impossible with compression only unless you're writing > only zeros or stuff alike. I don't know what bonnie uses for testing > but real life data doesn't compress 4 times. Two times, sometimes, All depends on your data. From a recent "compress the old logs" job on our syslog server: /logs/lennier.cc.vt.edu/2007/03/maillog-2007-0308: 85.4% -- replaced with /logs/lennier.cc.vt.edu/2007/03/maillog-2007-0308.gz And it wasn't a tiny file either - it's a busy mailserver, the logs run to several hundred megabytes a day. Syslogs *often* compress 90% or more, meaning a 10X compression. > but then it will be typically slower than disk access (I mean read, > as write will be much slower). Actually, as far back as 1998 or so, I was able to document 20% *speedups* on an AIX system that supported compressed file systems - and that was from when a 133mz PowerPC 604e was a *fast* machine. Since then, CPUs have gotten faster at a faster rate than disks have, even increasing the speedup. The basic theory is that unless you're sitting close to 100%CPU, it is *faster* to burn some CPU to compress/decompress a 4K chunk of data down to 2K, and then move 2K to the disk drive, than it is to move 4K. It's particularly noticable for larger files - if you can apply the compression to remove the need to move 2M of data faster than you can move 2M of data, you win. --==_Exmh_1175965831_4736P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFGF9CHcC3lWbTT17ARAkCjAKD9qQoON7KzBXuBY5sY/4zgVVfjHgCg8joB EhcogAGY+4wH4uLNqI0kTUE= =fj85 -----END PGP SIGNATURE----- --==_Exmh_1175965831_4736P--