Re: FCP target reset

James Bottomley
2009-08-04T16:20:28Z

On Tue, 2009-08-04 at 12:03 -0400, James Smart wrote:
>
> Douglas Gilbert wrote:
> > It looks like "target reset" is being phased out of SCSI
> > terminology and being partially replaced by "hard reset".
>
> Well, there's still an "I_T Nexus Reset" within the TMF area, which FCP-4
> provides no mapping for, but does define how to create a I_T Nexus loss event.
>
> Headache is there's history... SPI BDRs did full target resets and killed i/o
> for all initiators. Target Reset and FCP-2 gave same kind of semantic. FCP-3
> and later tried to make initiators better citizens and isolate reset semantics
> if possible. Unfortunately, there's lots of users that equate FC to SCSI, SCSI
> to SPI, and assume SPI-like semantics. So changing things just to be
> standard-compliant always seems to upset someone (and it's usually the most
> critical someone).

The headache with dropping TDR is going to be SCSI-2 reservations. They
need some type of reset to trigger release. LUN reset will do it, but
it's a new addition and we don't currently have a SG_SCSI_RESET_XXX
allocated to it so there's no way userland can request it at the moment.

James