SAS is the successor to SCSI, while SATA is the successor of Parallel-IDE-ATA.


Everyone says SAS is more „business“… just as SCSI was.

I have got 2x QNAPs (raid5) and 1x SERVER (raid10) running on enterprise SATA harddisks. Without hardware-related data loss for the last 5 years.

of course i get informed per mail, if a drive fails and there is always an replacement sata drive next to the device.

What i would consider a major disadvantage is that you CAN NOT CONNECT SAS DRIVES TO USB (to backup your files in case the raid driver died) while you can connect SATA drivers to USB with ease.

Also price-wise: you really feel ripped off when looking at SAS 3COM Controller prices. I wonder if you really get 10x to 30x times more performance for your money.

All these controller needs special device drivers… if the damn thing fails… and you are using raid… have fun getting a replacement card with the exact same firmware in order to get that thing back to work.

With software raid1 + sata harddisks (pretty easy to setup on debian and ubuntu) you don’t have that issue and most CPUs can handle software raid with ease.

Comparison with SATA

There is little physical difference between SAS and SATA.[2]

  • Systems identify SATA devices by their port number connected to the host bus adapter or by their Universally unique identifier (UUID), while SAS devices are uniquely identified by their World Wide Name (WWN).
  • SAS protocol provides for multiple initiators in a SAS domain, while SATA has no analogous provision.[2]
  • Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing,[2] each of which has its pros and cons.
  • SATA uses a command set that is based on the parallel ATA command set and then extended beyond that set to include features like native command queuing, hot-plugging, and TRIM. SAS uses the SCSI command set, which includes a wider range of features like error recovery, reservations and block reclamation. Basic ATA has commands only for direct-access storage. However SCSI commands may be tunneled through ATAPI[2] for devices such as CD/DVD drives.
  • SAS hardware allows multipath I/O to devices while SATA (prior to SATA 3Gb/s) does not.[2] Per specification, SATA 3Gb/s makes use of port multipliers to achieve port expansion. Some port multiplier manufacturers have implemented multipath I/O using port multiplier hardware.
  • SATA is marketed as a general-purpose successor to parallel ATA and has become common in the consumer market, whereas the more-expensive SAS targets critical server applications.
  • SAS error-recovery and error-reporting uses SCSI commands, which have more functionality than the ATA SMART commands used by SATA drives.[2]
  • SAS uses higher signaling voltages (800–1600 mV TX, 275–1600 mV RX) than SATA (400–600 mV TX, 325–600 mV RX). The higher voltage offers (among other features) the ability to use SAS in server backplanes.[2]
  • Because of its higher signaling voltages, SAS can use cables up to 10 m (33 ft) long, whereas SATA has a cable-length limit of 1 m (3.3 ft) or 2 m (6.6 ft) for eSATA.[2]