From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [linux-iscsi-devel] Re: [PATCH RFC] replace ioctl for sysfs take 2 Date: 07 Sep 2004 16:42:40 -0400 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <1094589763.2401.143.camel@mulgrave> References: <20040907191918.C045E76C56@isis.visi.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat16.steeleye.com ([209.192.50.48]:33236 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S268580AbUIGUpn (ORCPT ); Tue, 7 Sep 2004 16:45:43 -0400 In-Reply-To: <20040907191918.C045E76C56@isis.visi.com> List-Id: linux-scsi@vger.kernel.org To: "Scott M. Ferris" Cc: Mike Christie , Mike Christie , Matthew Wilcox , Christoph Hellwig , iscsi -devel , David Wysochanski , "Surekha.PC" , SCSI Mailing List On Tue, 2004-09-07 at 15:19, Scott M. Ferris wrote: > James Bottomley wrote: > > > > A host is the analogue of a bus. > > That's not a very helpful analogy, since only SPI and FC-AL resemble a > bus, and all of the newer SCSI transports are switched fabrics. Well, I'm at a bit of a loss to make it plainer ... a host is somewhere you plug your bus this is an obvious concept even for switched fabrics. The mid layer concept of the host is designed around managing the resources that come with such a physical attachment. However, since the iSCSI driver is virtual, it thinks more in terms of connected endpoints, so a bus becomes a representation of this virtual connection. But the question of where you want your resources managed seems to have the appropriate answer of "per connection". What you definitely don't want is to have the entire universe of iSCSI devices treated as a single set of resources to manage. > > In iSCSI that's really the other end point. Using abstractions > > incorrectly (like a single host for the entire iSCSI system) is > > bound to end up with problems due to the concept mismatch. > > I have trouble understanding your viewpoint. Your answers to the > following questions will hopefully clear things up. I doubt it, but I'll try. > Do you think Linux hosts should be used in a similar way by all > switched SCSI transports (e.g. FC-SW, iSCSI, SAS)? If not, why not? Yes. > Do you think switched SCSI transports should allocate one Linux host > for each I_T nexus? No. > Do you think switched SCSI transports should allocate one Linux host > for each (SAM-2 or SAM-3) SCSI initiator port? Yes. > Do you think switched SCSI transports should allocate one Linux host > for each (SAM-2 or SAM-3) SCSI initiator device? No. James