[stgt] [Scst-devel] [ANNOUNCE]: Comparison of features between different SCSI targets (SCST, STGT, IET, LIO) updated

[Nicholas A. Bellinger]

On Thu, 2010-09-02 at 15:00 -0500, Chris Weiss wrote:
> On Thu, Sep 2, 2010 at 2:31 PM, Vladislav Bolkhovitin <vst at vlnb.net> wrote:
> > Hello,
> >
> > I updated the Linux SCSI targets comparison page
> > http://scst.sourceforge.net/comparison.html, which compares features of
> > the existing Linux SCSI target subsystems. The comparison includes SCST,
> > STGT, IET and LIO. I added IET there, because it is the most used Linux
> > iSCSI target at the moment.
> .
> .
> >
> > If you see I'm wrong somewhere or forgot something, you are welcome to
> > correct me and I will fix that.
> >
> > Vlad
> >
> 
> as a user following the potential inclusion of a kernel-space target,
> iscsi specifically, I would be very interested in seeing what other
> pluses the other frameworks have over scst, because if this chart is
> accurate, all the other targets have quite a ways to go to catch up.
> 

Actually sorry, anyone who has spent more than 30 minutes looking at the
TCM v4 code that has already been posted to linux-scsi on monday knows
this list just more handwaving.  I suggest you start doing the same
(actually discussion specific source file + line refrences) unless you
actually want to trust this hopelessly out-of-date list on blind
princaple.

> To me, lacking correct reserve and task management means "not ready
> for public consumption".  Making any kernel change that does not have
> RESERVE/RELEASE and full TM command support is only going to make
> Linux look buggy and amateur-ish in the storage world.

First, understand that Vlad has been asked to produce a problem use case
for his CRH=1 (Compatibility Reservation Handling) concerns using the
SPC-3 RESERVE/RELEASE methods with the TCM v4 code.  He has been never
been able to produce a use case, ever.  Also, just for reference, does
SCST's SPC-3 persisent reservation handling actually properly support
CRH=1 emulation from spc4r17..?  Last time I checked, it most certainly
did *not*.

Second, in terms of TM emulation / passthrough support in the TCM v4
code, we follow what is implemented in drivers/scsi ML and LLDs,
primarly to properly for Linux SCSI Initiators.  I honestly don't have
alot of interesting currently in implementing all of the ancient TM
emulation that none of the mainline SCSI LLDs in Linux implement today,
or plan to do the future.  As for specific TM concerns, I am happy to
address then on a case by case basis with the appropiate use case.

Best,

--nab

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