From owner-freebsd-scsi@FreeBSD.ORG Wed Jun 23 15:18:19 2004 Return-Path: Delivered-To: freebsd-scsi@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 35BF716A4CE; Wed, 23 Jun 2004 15:18:19 +0000 (GMT) Received: from web.portaone.com (support.portaone.com [195.70.151.35]) by mx1.FreeBSD.org (Postfix) with ESMTP id 7210943D1F; Wed, 23 Jun 2004 15:18:18 +0000 (GMT) (envelope-from sobomax@portaone.com) Received: from portaone.com (localhost [127.0.0.1]) (authenticated bits=0) by web.portaone.com (8.12.8p2/8.12.8) with ESMTP id i5NFHqQO052374; Wed, 23 Jun 2004 17:17:56 +0200 (CEST) (envelope-from sobomax@portaone.com) Message-ID: <40D99F19.5010008@portaone.com> Date: Wed, 23 Jun 2004 18:17:45 +0300 From: Maxim Sobolev User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.4) Gecko/20030624 Netscape/7.1 (ax) X-Accept-Language: en-us, en, ru, uk MIME-Version: 1.0 To: =?ISO-8859-1?Q?S=F8ren_Schmidt?= References: <5.2.1.1.0.20040621135534.068fef40@server01.chassis00.xsnetworks.net> <40D7E0B7.1000905@portaone.com> <40D8D217.5000808@freebsd.org> <40D95FDC.9060802@portaone.com> <40D99D3B.8010608@DeepCore.dk> In-Reply-To: <40D99D3B.8010608@DeepCore.dk> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit cc: freebsd-scsi@freebsd.org cc: freebsd-current@freebsd.org Subject: Re: HostRaid support on FreeBSD X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Jun 2004 15:18:19 -0000 Søren Schmidt wrote: > Maxim Sobolev wrote: > >> Well, my knowelege about internals of software RAID controllers is >> quite limited, but as long as I know they are no more than BIOS with >> UI for setting up RAIDs and interface to main BIOS that hides internal >> RAID structure allowing to boot off the RAID. Also they provide some >> persistent storage for RAID configuration, I assume either in some >> controller's NVRAM or on the HDDs. Therefore, the same set of GEOM >> RAID modules can work with different software RAID controllers (SCSI, >> ATA, SATA etc) if there will be a standard way to extract this info >> from the controller's driver, and present it in some common format. >> That's what I am talking about. > > > Well, I dont know about SCSI, but ATA/SATA always stores the metadata on > disk, the controller has nothing todo with the RAID functionality, its > merely a way to talk to the disks. > > Reading the metadata off the disks and using that info to access a RAID > array is easy and can be had even without docs in a few hours. Writing > back the metadata in case of failures etc to retain sanity of the array > is "somewhat" more difficult. Actually I'm working with this currently > for new formats for ata-raid and its not trivial to get right. But I assume that on-disk format of this info and its location is controller-dependent, so that appropriate code to read/decode this info should probably be in the controller's driver. -Maxim