From owner-freebsd-hackers@FreeBSD.ORG Tue Dec 6 16:41:41 2005 Return-Path: X-Original-To: hackers@freebsd.org Delivered-To: freebsd-hackers@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id CB06916A41F for ; Tue, 6 Dec 2005 16:41:41 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from mh1.centtech.com (moat3.centtech.com [207.200.51.50]) by mx1.FreeBSD.org (Postfix) with ESMTP id 822BA43D9E for ; Tue, 6 Dec 2005 16:41:26 +0000 (GMT) (envelope-from anderson@centtech.com) Received: from [10.177.171.220] (neutrino.centtech.com [10.177.171.220]) by mh1.centtech.com (8.13.1/8.13.1) with ESMTP id jB6Gf4QA076781; Tue, 6 Dec 2005 10:41:04 -0600 (CST) (envelope-from anderson@centtech.com) Message-ID: <4395BF04.50101@centtech.com> Date: Tue, 06 Dec 2005 10:40:36 -0600 From: Eric Anderson User-Agent: Mozilla Thunderbird 1.0.7 (X11/20051204) X-Accept-Language: en-us, en MIME-Version: 1.0 To: hackers@freebsd.org Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: ClamAV 0.82/1204/Mon Dec 5 04:09:54 2005 on mh1.centtech.com X-Virus-Status: Clean Cc: Nate Lawson Subject: scsi-target and the buffer cache X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 06 Dec 2005 16:41:41 -0000 I'm curious about whether a target mode device would use the buffer cache or not. Here's a scenario: Host A: has fibre channel host adapter, in target mode, large memory pool, and another fiber channel host adapter connecting to fibre channel block device. Host B: Fibre channel host adapter, connecting to Host A. 'sees' the target mode block device created by Host A. Will Host A use the buffer cache to cache blocks between the real block device, and the shared target mode device? What about if Host A put a filesystem on the block device, created a single file the size of the filesystem, and shared that filesystem via a target mode device to Host B? What I'm wanting is a box (FreeBSD?) that can be placed between a fibre channel block device (like a RAID array), and a fibre channel host using that block device, and act as a block cache for that device, using the FreeBSD's memory. If it had a significant amount of memory, this could be very useful. Eric -- ------------------------------------------------------------------------ Eric Anderson Sr. Systems Administrator Centaur Technology Anything that works is better than anything that doesn't. ------------------------------------------------------------------------