Thanks for the reply. The app is some kind of digital artwork or rendering thing, which they currently run via some Apple servers. We did have it working using globalSAN without too many problems, but the two issues we found with that initiator were:
1- It wouldn't work with a 64bit kernel, the server had to be booted as a 32bit kernel
2- As far as I could tell the only way of getting the initiator to recognise a disk was to restart the session. This meant hot adding disks during production hours was not feasible.
The ATTO initiator is chargeable, so we weren't able to try it out.
Chris