From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Christie Subject: Re: [linux-iscsi-devel] Re: [PATCH RFC] replace ioctl for sysfs take 2 Date: Tue, 07 Sep 2004 14:12:32 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <413E2440.8080509@cs.wisc.edu> References: <20040907210520.0251476C56@isis.visi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from sabe.cs.wisc.edu ([128.105.6.20]:64152 "EHLO sabe.cs.wisc.edu") by vger.kernel.org with ESMTP id S268671AbUIGVWM (ORCPT ); Tue, 7 Sep 2004 17:22:12 -0400 In-Reply-To: <20040907210520.0251476C56@isis.visi.com> List-Id: linux-scsi@vger.kernel.org To: "Scott M. Ferris" Cc: James Bottomley , Mike Christie , Matthew Wilcox , Christoph Hellwig , iscsi -devel , David Wysochanski , "Surekha.PC" , SCSI Mailing List Scott M. Ferris wrote: > James Bottomley wrote: > >>On Tue, 2004-09-07 at 15:19, Scott M. Ferris wrote: >> >> >>>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. > > > So a host is where you plug your (non-existent) bus? I think it would > be clearer to use terminology from SAM. > > >>>>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. > > > Thanks. > > >>>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. > > > I'm glad we agree on that. > > >>>Do you think switched SCSI transports should allocate one Linux host >>>for each I_T nexus? >> >>No. > > > This is exactly why I ask these questions. The iSCSI driver > developers just implemented this, because they thought this is what > you and Christoph were asking for. Apparently it's not what you > wanted. Thank you for clarifying this. So we should go back to a single linux host, right? The iscsi session is an I_T nexus, so the only way to store the session state in the host is to allocate a session per host. > >>>Do you think switched SCSI transports should allocate one Linux host >>>for each (SAM-2 or SAM-3) SCSI initiator port? >> >>Yes. > > > Thank you. This is a much clear statement of your intent. > > >>>Do you think switched SCSI transports should allocate one Linux host >>>for each (SAM-2 or SAM-3) SCSI initiator device? >> >>No. > > > Should all drivers that currently use one host for each SCSI initiator > device, and a channel for each initiator port on each device, be > modified to use a host for each initiator port? > > Documentation/scsi/scsi_mid_low_api.txt says that a host corresponds > to a SCSI initiator device. Could someone change that to say SCSI > initiator port instead, since that seems to be the new goal? >