SAS (Serial Attached SCSI) is a computer bus technology primarily designed for transfer of data to and from computer data storage devices such as hard drives, CD-ROM… It is a replacement for parallel SCSI. It is also backwards-compatible with SATA drives. It uses serial communication instead of the parallel method but still uses SCSI commands.
SAS (Serial Attached SCSI) vs parallel SCSI
What is RAID 6? By the way, do you know what is RAID? RAID is also known as Redundant Arrays of independent drives. It is a technology that supports the integrated use of two or more hard-drives in various configurations for the purposes of achieving greater performance, reliability through redundancy, and larger disk volume sizes through aggregation.

It is like RAID 5 but with two parity blocks instead of one