scsi_target with multiple luns

[Scott Long]

Many companies use the scsi_target and targ code as a basis for 
prototyping and developing target code that is more suited to their
needs.

Scott


Hidetoshi Shimokawa 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
>> >
>> > _______________________________________________
>> > freebsd-scsi at freebsd.org mailing list
>> > http://lists.freebsd.org/mailman/listinfo/freebsd-scsi
>> > To unsubscribe, send any mail to "freebsd-scsi-unsubscribe at freebsd.org"
>> >
>>
>>
> 
>