How do you attach two suns to a single SSA?

[Judith Reed]

We have an ultra-2 attached to an SSA 200 series, utilizing only about
1/2 of the disks in the array. We'd like to attach a second ultra to the
array, such that:
	* it could use the unused disks on an everyday basis
	* in the event of a failure of the first ultra-2 the second system
		could import the volumes from the failed system and use
		them.
I understand that we cannot access the same disks from two systems at the
same time - this is not an issue.

A sun sales engineer said that we'd have to add a second controller to the
array, attach the second system to the second controller, attach half
the disks to the second controller, and thus not be able to import the other
disks. Do y'all agree with this?

system1-----------------------|array1-controller1--disjoint_set1
                              |
system2-----------------------|array1-controller2--disjoint_set2

 I thought that we could install a second port on the existing array
controller, connect the second system to it, and logically access disjoint 
sets of disks in the array, but with the ability to import the other 
system's volumes in the event of the failure of that system. 

system1ctrlr1----------------------|                  
                                   |array1-controller1
system2ctrlr2----------------------|                  
                                                      

I also had the impression that we could have the following config:

system1-ctrlr1----------|
system1-ctrlr2-------|  |
		     |  |----------|array1-controller1\
                     |             |                   \
                  |--|-------------|                    \ bunch of disks
                  |  |                                  / in one array
system2-ctrlr1----|--|--|                              /
system2-ctrlr2----|  |  |----------|array1-controller2/
                     |             |
                     |-------------|

(if we can't access disks in the array simultaneously from two systems
thru a single controller) such that the second connection to each controller
is just a hot-spare connection, to be used only in the event of a failure
of one or the other system - true???

TIA for any enlightenment you can provide...

-- 
Judith Reed
jreed@appliedtheory.com