From owner-freebsd-database@FreeBSD.ORG Sun Jan 22 10:49:44 2006 Return-Path: X-Original-To: freebsd-database@FreeBSD.ORG Delivered-To: freebsd-database@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id B15A616A41F for ; Sun, 22 Jan 2006 10:49:44 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (lurza.secnetix.de [83.120.8.8]) by mx1.FreeBSD.org (Postfix) with ESMTP id DDF6C43D45 for ; Sun, 22 Jan 2006 10:49:43 +0000 (GMT) (envelope-from olli@lurza.secnetix.de) Received: from lurza.secnetix.de (ytmlif@localhost [127.0.0.1]) by lurza.secnetix.de (8.13.4/8.13.4) with ESMTP id k0MAna0b089478 for ; Sun, 22 Jan 2006 11:49:42 +0100 (CET) (envelope-from oliver.fromme@secnetix.de) Received: (from olli@localhost) by lurza.secnetix.de (8.13.4/8.13.1/Submit) id k0MAnaVh089477; Sun, 22 Jan 2006 11:49:36 +0100 (CET) (envelope-from olli) Date: Sun, 22 Jan 2006 11:49:36 +0100 (CET) Message-Id: <200601221049.k0MAnaVh089477@lurza.secnetix.de> From: Oliver Fromme To: freebsd-database@FreeBSD.ORG In-Reply-To: <20060119011550.GN17896@decibel.org> X-Newsgroups: list.freebsd-database User-Agent: tin/1.8.0-20051224 ("Ronay") (UNIX) (FreeBSD/4.11-STABLE (i386)) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.1.2 (lurza.secnetix.de [127.0.0.1]); Sun, 22 Jan 2006 11:49:42 +0100 (CET) Cc: Subject: Re: Horrible PostgreSQL performance with NFS X-BeenThere: freebsd-database@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: freebsd-database@FreeBSD.ORG List-Id: Database use and development under FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 22 Jan 2006 10:49:44 -0000 Jim C. Nasby wrote: > On Wed, Jan 18, 2006 at 05:11:15PM -0800, Brooks Davis wrote: > > On Wed, Jan 18, 2006 at 06:58:47PM -0600, Jim C. Nasby wrote: > > > On Sat, Jan 14, 2006 at 06:42:02AM -0800, Arne Woerner wrote: > > > > Did you do those "dd" tests with small block sizes (like 1byte: > > > > bs=1), like somebody on one of those lists suggests, too? Then we > > > > could see, if there is a high latency that ruins everything... > > > > > > FYI, PostgreSQL does 8kB I/O by default. This can only be changed by > > > modifying a header file. > > > > That's definitely small in my book (certainly compared to the 1MB block > > size the first responder suggested), knowing that, you should > > definitely do dd tests with 8k blocks since that's the best performance you > > are likely to get. > > Agreed, it is small from a OS/filesystem viewpoint, but it's also > nowhere near 1 byte which is the test that had been suggested. :) FWIW, there is _no_ blocksize that can be used wit dd(1) that benchmarks disks the same way a database does. Unless our dd(1) implemetation grew a random-seek option that I missed. :-) But seriously... dd(1) is NOT a benchmark. Never ever. Especially if you're interested in database performance. Best regards Oliver -- Oliver Fromme, secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing Dienstleistungen mit Schwerpunkt FreeBSD: http://www.secnetix.de/bsd Any opinions expressed in this message may be personal to the author and may not necessarily reflect the opinions of secnetix in any way. "If you aim the gun at your foot and pull the trigger, it's UNIX's job to ensure reliable delivery of the bullet to where you aimed the gun (in this case, Mr. Foot)." -- Terry Lambert, FreeBSD-hackers mailing list.