I'm doing the planning for the installation of a new EMC VNX5800 and want to upgrade my 5300 fabric switches to a higher, stable FOS level. They are currently on v6.3.1a. Is there a document to tell me this and where do I find it?
you could always try E-Lab Interoperability Navigator if you want to check the Interoperablity between brocade & emc hardware.
That might give you recommended FOS options available .
Even though 5300 supports FOS 7, current EMC target version for that switch model is 6.4.3d. So I would recommend you to go to that version.