CX3-10F/NS-20 Upgrade questions

Hello:  We have a Celerra CX3-10f (which is also known as an NS20?).  Currently it has 2 storage processors and 5 DAE's, and we are wanting to add a 6th DAE.  According to this post it can be upgraded to 90 drives:  https://community.emc.com/thread/99564 .  Our unit currently is on FLARE 3.26.10.5.019, PROM 3.58.00, and Agent 6.26.7.0.87. 

Does anyone know if it is possible to do the software updates with out having to completely power off the unit?  I seem to recall an option to fail over all the LUN's to one of the storage processors, then do the upgrade on the other processor.  Once that processor is back online, fail the LUN's to it and follow the same procedure for the other processor.

Basically I am trying to avoid any downtime for the SAN while I am upgrading it..

Any suggestions?

Thanks

Chris