Not sure what you mean here. A SAN is a Storage Area Network. You can’t run AD FSMO roles on a SAN. You can setup your DC to store it’s AD database on the SAN which will work fine. And you can run the FSMO roles on a domain controller which is using the SAN for storage also with no problem. But there is no way to run FSMO roles directly on a SAN as a SAN doesn’t have an OS which you can make a domain controller.