We have been using a HP EVA 4000 fc-san now for 5 years, without having any problems, but the time is here to invest in a new san. We have decided for a EVA 6400 fc-san (with iSCSI), and intend to migrate all existing data over to the new system.
We have about 5 ESX hosts and 80 VMs. We have 6 shared storage LUNs for the ESX hosts, and use about 50 Raw Device Mapping (RDM)(physical).
The main reason for buying a new EVA, is the ability to use 90-days migration license for "continous access". This enables the old EVA to mirror (one way, old => new) LUNs over to a new EVA. I dont know wheter WWN og LUN-number are migrated. Then i just power down the whole vmware farm, stop the mirror (makes the new EVA read-write) and connects the vmware-farm to the new fabric (already zoned).
So over to the main problem:
I guess the shared storage reference by data on the disks, partition ID's or something, so i don't think these will make problems
I need to know how a RDM are referenced, are they referenced by "some data on the disk", by WWN, by LUN-number or something else?
Another solution is to use storage vmotion, by connection the ESX-servers to BOTH FC-fabrics, creating new shared storage on the new san, and moving server by server. I then have to mirror the RDMs, and re-connect them after the migration of each VM.
Two important aspects you may want to ask yourself are "how quickly do I want to move" and "do I want to rebalance what VM's are in what datastores." The answers to these two questions will largely in part drive which migration approach makes the most sense for you.