From owner-freebsd-fs@FreeBSD.ORG Thu Jun 29 10:47:08 2006 Return-Path: X-Original-To: freebsd-fs@freebsd.org Delivered-To: freebsd-fs@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 2B62D16A410 for ; Thu, 29 Jun 2006 10:47:08 +0000 (UTC) (envelope-from bde@zeta.org.au) Received: from mailout1.pacific.net.au (mailout1.pacific.net.au [61.8.0.84]) by mx1.FreeBSD.org (Postfix) with ESMTP id 844A843D69 for ; Thu, 29 Jun 2006 10:47:06 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailproxy1.pacific.net.au (mailproxy1.pacific.net.au [61.8.2.162]) by mailout1.pacific.net.au (Postfix) with ESMTP id 7C3AD24D0A8; Thu, 29 Jun 2006 20:47:05 +1000 (EST) Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246]) by mailproxy1.pacific.net.au (8.13.4/8.13.4/Debian-3sarge1) with ESMTP id k5TAl3XM008341; Thu, 29 Jun 2006 20:47:04 +1000 Date: Thu, 29 Jun 2006 20:47:03 +1000 (EST) From: Bruce Evans X-X-Sender: bde@delplex.bde.org To: Leo Huang In-Reply-To: Message-ID: <20060629201157.N77878@delplex.bde.org> References: <44A1B958.4030204@fer.hr> <20060628230439.M75051@delplex.bde.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: freebsd-fs@freebsd.org, Ivan Voras Subject: Re: Is the fsync() fake on FreeBSD6.1? 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, 29 Jun 2006 10:47:08 -0000 On Thu, 29 Jun 2006, Leo Huang wrote: >> >> OS Clients Result(queries per second) TPS(got from >> >> iostat) >> >> FreeBSD6.1 50 516.1 about 2000 >> >> Seems normal for drives that do write caching. > > I disable the driver write caching as Bjorn Gronvall suggest, the > result show that the TPS come down to about 200. So I think you and > Bjorn Gronvall are right. It is the disk write caching make the TPS so > high. > >> >> Debian3.1 50 49.8 about 200 >> >> Seems to slow for disks that do write caching. Maybe Debian does something >> to force the drive to complete it's i/o, or just does a full sync() like >> someone mentioned Linux doing. > > I use sginfo the find that the disk write caching is also enabled > default. After the disk write caching is disabled, the TPS also come > down from 200 to 110. This is really pullze me. Can you give me more > infomation about it? How did you disable "driver" write caching? I think both Bjorn and I meant the _drive_ write caching, and that is what you refer to as "disk" write caching. Only turn off the caching in the lowest layer (disk == drive). I wonder when all drives will have enough fast enough nonvolatile RAM for write caching to just work. Bruce