For each target, we support 254 LUNs. Each HBA can support 128 Targets per “Bus” where bus might be an artificial construct, and there could be 8 buses per HBA (officially). So, per HBA (theoretical):
254 * 128 * 8 = 260,096 LUNs per HBA
The system will run out of resources long before that and each HBA will not be able to support anything close to that. Also, there can be 255 HBAs per system although I have not seen a system that had resources for more than 30.