From owner-freebsd-hackers@FreeBSD.ORG Thu Dec 8 08:16:29 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 0F61516A41F for ; Thu, 8 Dec 2005 08:16:29 +0000 (GMT) (envelope-from nate@root.org) Received: from www.cryptography.com (li-22.members.linode.com [64.5.53.22]) by mx1.FreeBSD.org (Postfix) with ESMTP id C710A43D79 for ; Thu, 8 Dec 2005 08:16:19 +0000 (GMT) (envelope-from nate@root.org) Received: from [172.16.0.224] (fi01-84CBdd.tokyo.flets.isao.net [211.132.203.221]) by www.cryptography.com (8.12.8/8.12.8) with ESMTP id jB88GKdu025083 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NOT); Thu, 8 Dec 2005 00:16:23 -0800 Message-ID: <4397EBC7.9030105@root.org> Date: Thu, 08 Dec 2005 17:16:07 +0900 From: Nate Lawson User-Agent: Mozilla Thunderbird 1.0.6 (Windows/20050716) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Scott Long References: <4395BF04.50101@centtech.com> <43960F55.3010508@root.org> <43975926.1010302@centtech.com> <43975F5F.5080901@samsco.org> <439782AA.6000408@root.org> <4397B731.6010308@centtech.com> <4397B82C.5020004@samsco.org> In-Reply-To: <4397B82C.5020004@samsco.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Mailman-Approved-At: Thu, 08 Dec 2005 12:27:28 +0000 Cc: hackers@freebsd.org, Eric Anderson Subject: Re: 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: Thu, 08 Dec 2005 08:16:29 -0000 Scott Long wrote: > Eric Anderson wrote: > >> Nate Lawson wrote: >>> Agree 100%. While having it in usermode means there are boundary >>> crossings that increase per-transaction latency, the actual bulk data >>> transfer is via zero-copy IO and you should be able to exceed the >>> data transfer rates of several 10K RPM drives on decent hardware. >> >> Ok, great.. Now, will scsi_target work ok with raw devices, or only >> files? (although I'm not sure theres all that much difference really). >> > > You can write your userland code to use whatever files or devices you > want. Are you talking about the scs_target.c code in > /usr/share/examples? That's just a skeletal example that you can use > as a starting point for your own work. No, it's not just a skeletal example. You can point it at a raw device as the backing store file and it will work as a block device (i.e. RBC command set). It has been tested as working at least moderately fast over SCSI, FC, and firewire. -- Nate