Like how quick SATA hard drives took off, Serial Attached SCSI (SAS) has grown exponentially in 2006 going by this BusinessWire report.  The SCSI Trade Association which supports and promotes SCSI technology announced that SAS is set to take over Ultra320 SCSI this year as the preferred interface choice in standard high volume servers.  According to a Gartner research report that covers the multi-user SAS HDD market, SAS drives accounted for 11.2% of all multi-user HDDs in use in 2006.  It predicts that 12 million SAS HDDs will ship this year, up from nearly 4.5 million units sold up to the end of 2006.

So far, parallel SCSI has dominated the server market for over 20 years.  From late 2008, Gartner Dataquest expects 6Gbps SATA to start taking over from the current 3Gbps SATA drives.  When it comes to the drives themselves, the market for small form factor (SFF) hard disks is also growing for enterprise environments due to their lower power usage over the traditional 3.5" drives. 

Further info can be read in this BusinessWire Report.