From owner-freebsd-current@FreeBSD.ORG Thu May 26 17:53:20 2005 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 17FC116A41C for ; Thu, 26 May 2005 17:53:20 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from mh2.centtech.com (moat3.centtech.com [207.200.51.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id ADB6D43D53 for ; Thu, 26 May 2005 17:53:19 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from [10.177.171.220] (neutrino.centtech.com [10.177.171.220]) by mh2.centtech.com (8.13.1/8.13.1) with ESMTP id j4QHrHxr053808; Thu, 26 May 2005 12:53:17 -0500 (CDT) (envelope-from anderson@centtech.com) Message-ID: <42960CFE.4060307@centtech.com> Date: Thu, 26 May 2005 12:53:02 -0500 From: Eric Anderson User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.7) Gecko/20050504 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Bjoern Koenig References: <4295D51F.50106@centtech.com> <429606D9.6080602@cs.tu-berlin.de> <42960ACB.7090801@cs.tu-berlin.de> In-Reply-To: <42960ACB.7090801@cs.tu-berlin.de> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Cc: FreeBSD Current Subject: Re: Disable read/write caching to disk? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 26 May 2005 17:53:20 -0000 Bjoern Koenig wrote: > Bjoern Koenig wrote: > >> Eric Anderson wrote: >> >>> Is it possible to disable all read and write caching to a disk? >> >> >> You can disable write the cache by adding the line >> >> hw.ata.wc="0" > > > I assumed that you use ATA. If you use SCSI devices then read at least > the manpages da(4) and camcontrol(8). Thanks.. I've just read (quickly) both man pages. It seems as though you are suggesting disabling the physical disk caching, which should not make a difference in my case. The disk would report whatever it needs to report to either host, and those should be in sync. When I mount the filesystem on host B ro, it shows me the filesystem as of the time that I mounted it ro. Any subsequent changes on host A (which has it mounted rw) are not seem on host B unless I unmount and mount again on host B. This seems like a FreeBSD feature and not a general scsi feature. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology A lost ounce of gold may be found, a lost moment of time never. ------------------------------------------------------------------------