From owner-freebsd-geom@FreeBSD.ORG Fri Apr 23 14:40:49 2010 Return-Path: Delivered-To: freebsd-geom@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 036321065703 for ; Fri, 23 Apr 2010 14:40:49 +0000 (UTC) (envelope-from ticso@cicely7.cicely.de) Received: from raven.bwct.de (raven.bwct.de [85.159.14.73]) by mx1.freebsd.org (Postfix) with ESMTP id 6551E8FC1F for ; Fri, 23 Apr 2010 14:40:47 +0000 (UTC) Received: from mail.cicely.de ([10.1.1.37]) by raven.bwct.de (8.13.4/8.13.4) with ESMTP id o3NE42es042161 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Fri, 23 Apr 2010 16:04:03 +0200 (CEST) (envelope-from ticso@cicely7.cicely.de) Received: from cicely7.cicely.de (cicely7.cicely.de [10.1.1.9]) by mail.cicely.de (8.14.3/8.14.3) with ESMTP id o3NE3xUJ024177 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 23 Apr 2010 16:03:59 +0200 (CEST) (envelope-from ticso@cicely7.cicely.de) Received: from cicely7.cicely.de (localhost [127.0.0.1]) by cicely7.cicely.de (8.14.2/8.14.2) with ESMTP id o3NE3xdX007705; Fri, 23 Apr 2010 16:03:59 +0200 (CEST) (envelope-from ticso@cicely7.cicely.de) Received: (from ticso@localhost) by cicely7.cicely.de (8.14.2/8.14.2/Submit) id o3NE3w5n007704; Fri, 23 Apr 2010 16:03:58 +0200 (CEST) (envelope-from ticso) Date: Fri, 23 Apr 2010 16:03:58 +0200 From: Bernd Walter To: John Baldwin Message-ID: <20100423140358.GC1575@cicely7.cicely.de> References: <4BD06BD9.6030401@FreeBSD.org> <201004230950.33999.jhb@freebsd.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <201004230950.33999.jhb@freebsd.org> X-Operating-System: FreeBSD cicely7.cicely.de 7.0-STABLE i386 User-Agent: Mutt/1.5.11 X-Spam-Status: No, score=-2.9 required=5.0 tests=ALL_TRUSTED=-1, BAYES_00=-1.9, T_RP_MATCHES_RCVD=-0.01 autolearn=ham version=3.3.0 X-Spam-Checker-Version: SpamAssassin 3.3.0 (2010-01-18) on spamd.cicely.de Cc: Alexander Motin , freebsd-current@freebsd.org, freebsd-geom@freebsd.org Subject: Re: Switchover to CAM ATA? X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: ticso@cicely.de List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 23 Apr 2010 14:40:49 -0000 On Fri, Apr 23, 2010 at 09:50:33AM -0400, John Baldwin wrote: > On Thursday 22 April 2010 11:31:37 am Alexander Motin wrote: > > If ataraid(4) should be reimplemented in GEOM, then how exactly? One > > more separate RAID infrastructure in GEOM (third?) looks excessive. > > Reuse gmirror, gstripe,... code would be nice, but will make them more > > complicated and could be not easy for RAID0+1 (due to common metadata) > > and RAID5 (due to lack of module in a base system). > > Scott's view (which sounds good to me) is that GEOM should include a library > of routines for working with common transforms such as RAID1, striping, etc. > Each ATA RAID vendor format would then consist of a small GEOM module that > used the library routines to manage all the I/O and the bulk of the module > would be managing a specific metadata format. I remember that SCSI standard has support for xor read-modify-write operations in addition to normal read/write to reduce R5 latency and bandwith. I'm not sure if any devices actually support it, but I think this may be worthwhile for networked devices. -- B.Walter http://www.bwct.de Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.