scsi_target with multiple luns

[Matthew Jacob]

Yes. None of the extant stuff is deployable as solid solution without reworking.

On 5/31/07, Hidetoshi Shimokawa <simokawa at freebsd.org> wrote:
> Yes, scsi_target(8) is an example.
> But the problem I described is actually a problem of targ(4)  (scsi_target.c).
> The userland can do nothing about this problem.
> Or do you mean targ(4) is also an example?
>
> On 6/1/07, Matthew Jacob <lydianconcepts at gmail.com> wrote:
> > Remember that scsi_target is an example. A fine example, but an
> > example. Having a single user process that can be shot and killed, no
> > matter how multithreaded or AIO'd, is not necessarily the wisest
> > choice for building a target device.
> >
> >
> > On 5/31/07, Scott Long <scottl at samsco.org> wrote:
> > > Hidetoshi Shimokawa wrote:
> > > > I have not fully analyzed the problem but I'll describe it just for a note.
> > > > I'd like to ask maintainers of scsi_target for further analysis.
> > > >
> > > > I experiance a problem with small number(1) of simq and multiple
> > > > scsi_target(8) instances.
> > > >
> > > > As far as I understand, the following situation could occur under a fairly
> > > > heavy load.
> > > >
> > > > 1. process A send a request -> cam send to sim
> > > > 2. process B send a request -> blocked because the simq is full
> > > > 3. the request of process A is finished (in the context of process A)
> > > > 4. cam/scsi_target tries to send the request of process B.
> > > >    But the mapped memory is of process A, and scsi_target send wrong
> > > >    ccb to sim.
> > > >
> > > > Maybe, we should rewrite scsi_target in kernel space with GEOM support..
> > >
> > > I'm unclear on how GEOM would fix this.  Also, scsi targets aren't
> > > always DA devices.  I dedicated scsi_da_target device that is backed
> > > by GEOM might be interesting, though.  Even more interesting would be
> > > a direct DMA method that required no KVA mappings for the data.
> > >
> > > Scott
> > >
> > > _______________________________________________
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> > >
> >
> >
>
>
> --
> /\ Hidetoshi Shimokawa
> \/  simokawa at FreeBSD.ORG
>