Clearing effects of logouts on different protocols

Robert Snively rsnively at Brocade.COM
Tue Mar 5 10:03:07 PST 2002

* From the T10 Reflector (t10 at, posted by:
* Robert Snively <rsnively at>
>Bob (at al) - 

>I can agree with your desire to strongly discourage classic 
>Reserve/Release for contemporary environments. The avoidance 
>of this mechanism conveniently sidesteps any adverse effects 
>of the clearing effects of (for instance) PLOGI upon 

>However, the issue I posted yesterday still stands. For 
>better or worse (admittedly mostly for worse), SCSI has 
>traditionally allowed for specifying (for instance) the 
>current partition upon a tape through the use of MODE 
>SELECT. To reiterate, due to this fact, booting a 
>workstation on a SAN may lead to data loss. Note that, 
>unlike the case of the reservation issue, there is no 
>way to guard against this issue, unless FCP-2 clearing 
>effects are redefined. 

	Folks, fortunately, this is addressed by the recommended
	treatment of MODE SELECT established parameters in
	tape drives.  While "saved" parameters are recommended,
	implicit default parameters established by the
	state information about the tape (including position,
	compression parameters, and presumably partition
	information) should now be required.

>More fundametally, there exists an architectural layering 
>issue. Why should activities at the port layer effect 
>changes at the logical unit layer? I contend that this 
>is an encapsulation issue, violating commonly accepted 
>layering principles.

	There is a lot of discussion that can be had about this.

>If a host coming online wants to count on a known initial 
>state of an FCP-x device, they always have the ability to 
>perform PLOGI/PRLI/LOGICAL UNIT RESET. The clearing effects 
>of login are not necessary for this funcitonality.
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