From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Reinecke Subject: Re: [LSF/MM TOPIC] Unifying the LIO and SCST target drivers Date: Wed, 14 Jan 2015 12:26:48 +0100 Message-ID: <54B65278.1030406@suse.de> References: <54B63F74.2040702@sandisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <54B63F74.2040702@sandisk.com> Sender: target-devel-owner@vger.kernel.org To: Bart Van Assche , "lsf-pc@lists.linux-foundation.org" Cc: "linux-scsi@vger.kernel.org" , target-devel , "Nicholas A. Bellinger" List-Id: linux-scsi@vger.kernel.org On 01/14/2015 11:05 AM, Bart Van Assche wrote: > The LIO and SCST SCSI target subsystems consist of the following comp= onents: > * A core that processes SCSI commands and that provides common > functionality like persistent reservations, LUN masking and an interf= ace > that allows configuration from user space. > * Device handlers that allow this core to access SCSI devices, block > devices and files uniformly as SCSI devices. > * Target drivers that implement a storage protocol (iSCSI, FC, SRP, > iSER, FCoE, ...) and that realize the SCSI request and response > communication between the target system and an initiator system. >=20 > A significant amount of code is shared between several LIO target > drivers and the SCST target drivers that implement the same storage > protocol. Since there are two sets of these drivers this means that e= ach > set has to be maintained, extended and tested separately. This means = a > lot of redundant work. The main difference between these two sets of > drivers is the interface between the target drivers and the SCSI targ= et > core. Hence the proposal to discuss the unification of the API betwe= en > SCSI target core and SCSI target drivers. Implementing a single unifi= ed > API would have the following advantages: > * A single set of target drivers works for both projects which means = a > reduction of the maintenance effort for those who maintain target > drivers for target driver developers and target driver users. > * This would increase the size of the user base for the unified targe= t > drivers. > * This would reduce the workload for the storage target maintainers. > * This would motivate the SCST target driver maintainers to contribut= e > to the upstream target drivers and to bring the upstream SRP and FCoE > target drivers to the same feature and stability level as their SCST > counterparts. In other words, the LIO users would also benefit from t= his > work. > * This effort would also help SCST users by ensuring that all latest > target driver features are also available to SCST users. Some time ag= o > (but no longer today) the LIO QLogic target driver was ahead of the S= CST > QLogic target driver. This motivated an SCST user to port the LIO QLo= gic > target driver to SCST. See also Greg Wettstein, New release of > SCST/Qlogic target interface driver, linux-scsi, April 2014, > http://marc.info/?l=3Dlinux-scsi&m=3D139649571807085). >=20 > During the first phase of this initiative the focus will be on the > QLogic FC, SRP and FCoE target drivers since a significant part of th= e > code of these drivers is shared between the two target frameworks. >=20 > For those who are not following the SCST project: I'm maintaining the > SCST SRP and FCoE target drivers. >=20 > Nic, in case it was not yet clear, you would be more than welcome dur= ing > this session :-) >=20 I'd like to have this discussion, too. It would be really good if we can make that work; after all, Linux should be about _choice_. So if both parties agree to have this discussion I'm all for it. I can even act as a moderator if required :-) Cheers, Hannes --=20 Dr. Hannes Reinecke zSeries & Storage hare@suse.de +49 911 74053 688 SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N=C3=BCrnberg GF: F. Imend=C3=B6rffer, J. Smithard, J. Guild, D. Upmanyu, G. Norton HRB 21284 (AG N=C3=BCrnberg)