SAN based storage allows multiple computers to assess the storage devices simultaneously so it is down to how much have you got to send vs. what do you need in terms of performance.
What is needed is something like the OCSF2 file system and a locking daemon to ensure the data and meta data does not get corrupt. If the storage is shared the file system need to support shared access.
SLE HA supports two cluster aware file systems, OCFS2 and GFS2 (lecture p546 - ). They also need DLM or cLVM or both. SUSE recommends OCFS2 over GFS2.
The choice of SAN is down to you and I am sure there are comparative studies of iscsi vs fiber channel vs fiber channel over ethernet out there somewhere, probably from storage vendors. This article seems a good place to start.