On Tue, 10 May 2011, Ben Rockwood wrote:
I have a mirror-mode configuration between two nodes in a single data center now. I'd like to expand this to 2 additional data centers. The intent would be to have read-only HA pairs in each of the new data centers that will continue to function even if the data center is cut off from the primary pair.
I'm not clear as to what you're looking to install in your new locations. The wording ("read-only HA pairs") implies additional mirrormode installations, but I don't think that makes sense if you are specifying read-only capability. If your concern is additional read-only capacity then you should just be expanding your replica pool, nothing more. This is true regardless of whether you desire on-site or off-site read-only capacity.
Please see the diagram in the Admin Guide, section 18.3.4.1.1. Actually, if you're revisiting your architecture, rereading the entire chapter may be in order...