Features that differentiate between HBA products include: Multiple ports supporting redundant and/or aggregated data paths. Port speed
Most HBAs sold today are 4Gb/s but there are still 2Gb/s HBAs on the market. Most HBA vendors now have 8Gb/s FC support.
Use of removable transceivers SFPs provide more flexibility than fixed interfaces but can cost more.
Automatic failover To another port on the same HBA or to a different HBA in the same host. HBA vendors typically supply multipathing drivers for their HBAs, but these drivers offer varying levels of functionality. Criteria include failover time, recovery capability, and support for load- levelling (manual path selection or dynamic path selection).
Support for protocols other than SCSI-FCP, including IP and VI.
Support for multiple Classes of Service Many HBAs support only Class 3, but others support Classes 2 and 3.
FC-Tape Profile Support is required for interoperability with some native FC tape libraries and drives.
The ability to boot a host from a remote SAN-attached disk.