The SCSI Trade Association which manages the standard SAS (Serial Atached SCSI) used in environments where performance is crucial, announced a new variation of the standard. It pushes the maximum data flow from 3 to 6 Gbits/s, and takes again the lead from the little expensive SATA II.
Even though SAS is not used by the general public, it remains accessible to the owners of the Mac Pro, who can use such disks by installing a RAID card. In addition to higher capacities, SAS has other advantages, like consuming less processor resources and proposing hard disks that are (more expensive) faster and more robust, which is not a bad thing seeing the lifespan of certain SATA disks.
[translation by crispin]