From owner-freebsd-scsi@FreeBSD.ORG Wed Jun 2 06:12:02 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 3230216A4CE for ; Wed, 2 Jun 2004 06:12:02 -0700 (PDT) Received: from panzer.kdm.org (panzer.kdm.org [216.160.178.169]) by mx1.FreeBSD.org (Postfix) with ESMTP id 63F2343D46 for ; Wed, 2 Jun 2004 06:12:00 -0700 (PDT) (envelope-from ken@panzer.kdm.org) Received: from panzer.kdm.org (localhost [127.0.0.1]) by panzer.kdm.org (8.12.9/8.12.5) with ESMTP id i52DBtui077167; Wed, 2 Jun 2004 07:11:55 -0600 (MDT) (envelope-from ken@panzer.kdm.org) Received: (from ken@localhost) by panzer.kdm.org (8.12.9/8.12.5/Submit) id i52DBrNS077164; Wed, 2 Jun 2004 07:11:53 -0600 (MDT) (envelope-from ken) Date: Wed, 2 Jun 2004 07:11:53 -0600 From: "Kenneth D. Merry" To: David Malone Message-ID: <20040602131153.GA77049@panzer.kdm.org> References: <200406012304.i51N4pV4013286@himinbjorg.tucs-beachin-obx-house.com> <20040601234010.GA72828@panzer.kdm.org> <20040602094939.GA48588@walton.maths.tcd.ie> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040602094939.GA48588@walton.maths.tcd.ie> User-Agent: Mutt/1.4.1i cc: freebsd-scsi@freebsd.org Subject: Re: 1TB issue 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, 02 Jun 2004 13:12:02 -0000 On Wed, Jun 02, 2004 at 10:49:39 +0100, David Malone wrote: > On Tue, Jun 01, 2004 at 05:40:10PM -0600, Kenneth D. Merry wrote: > > See another recent message on this list from Brooks Davis. It sounds like > > sysinstall has issues with large arrays in -current, but fdisk works okay. > > I've heard from some people that there was a 2TB limit on SCSI > devices, but it wasn't clear to me if this was a limit of the SCSI > implementation they were using, or if it arose from the SCSI spec. > What's actually the case here? It's a limitation in the device they're using and/or the SCSI layer they're using. With 10 or 12 byte read/write CDBs, you're limited to 32 bits to specify the LBA. For a device with 512 byte sectors, that limits you to 2TB. With the SBC-2 spec, they (T10) introduced 16 byte read, write and read capacity commands. That allows you to get the size of a device larger than 2TB, and address blocks past the 2TB limit. (The size of the LBA field was increased to 8 bytes for the 16 byte commands, so you can address 2^64 blocks.) CAM in FreeBSD-current has had support for devices larger than 2TB for a little over a year. -stable doesn't have that support, because it has other limitations (pointed out by Bruce) that basically mean CAM support for large devices wouldn't really matter. Ken -- Kenneth Merry ken@kdm.org