Serial Attached SCSI

(sass)

SCSI, initially, was a parallel connection. The parallel connection version of SCSI will continue for some years to come but by mid-2005 serial attached SCSI (SAS) was being introduced and is expected to take over the market for new SCSI connections over time.

SAS is targeted to the market between high-performance fiber and lower-cost serial ATA storage for servers. Connections are point-to-point which allows for faster performance and better scalability. Point-to-point connections also allow easier troubleshooting as the defective device will be obvious instead of just one among up to 16 devices on a bus.

Drive revolution speed in drives introduced in 2005/2006 is in the 10,000-15,000 rpm range; faster than the 7,200 rpm of other drive types. Drives come in 3.5-inch and 2.5-inch sizes; the latter designed for the smaller form factor of blade servers.

Initial speeds are specified to be 3Gbps full-duplex and the next generation, expected in the 2007 timeframe, will likely be specified to be 6Gbps full-duplex. Cable length for a SAS system maxes out at around 6 meters.

SAS will not interoperate with current parallel SCSI devices.

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