Re: Persistent reservation behaviour/compliance with redundant controllers

[James Bottomley <James.Bottomley@HansenPartnership.com>]

On Mon, 2014-01-06 at 23:53 +0100, Matthias Eble wrote:
> 2014/1/6 Lee Duncan <lduncan@suse.com>:
> > On 12/25/2013 03:00 PM, Matthias Eble wrote:
> >> Here's the dmmp map
> >> 360002ac0000000000000000a00006e6b dm-6 3PARdata,VV
> >> size=2.0T features='0' hwhandler='0' wp=rw
> >> `-+- policy='round-robin 0' prio=1 status=active
> >>   |- 3:0:1:4  sdg  8:96    active ready running
> >>   |- 3:0:3:4  sdl  8:176   active ready running
> >>   |- 5:0:3:4  sdbg 67:160  active ready running
> >>   `- 5:0:1:4  sdce 69:32   active ready running
> >>
> >> There can only be two registrations at a time: (sdg XOR sdl) and (sdbg XOR sdce)
> >> Now my question is: Does this comply to the standard?
> >>
> >
> > I _believe_ the problem is that you are re-registering the same
> > I_T_Nexus through /dev/sdl, your second attempt at registration, as you
> > did when you used /dev/sdg, your original registration.
> 
> 
> Can sdg and sdl be the same I_T_Nexus at a time?
> Right now, they are handled like that.
> In my understanding, every scsi disk device represents an I_T_Nexus.

No, every SCSI disk is an I_T_L nexus.  There's no actual device object
in Linux for an I_T nexus.

James