[CentOS] SCSI, SAS and FC Controller

Greetings,

Currently, we have several Direct Attached Storage (DAS) units, connected to respective servers through Adaptec SCSI Controller.

1) Most of the time we used 80Mbit/s for external SCSI devices (in this case, the DAS itself). Is it true the maximum speed for external SCSI devices would be up to 80Mbit/s? Tried to change to 320Mbit/s but somehow the kernel crashed. Is there any specific reason why some (or all) external devices can only go up to 80Mbit/s?

2) We were thinking to use SAS or FC HBA for our next DAS but I'm not sure which brand/card does has the support in CentOS/Linux in terms of kernel module/driver,compatibility and performance. Can anyone give suggestions based on their experience?

TIA.

-Ikmal