Difference Between SATA and SAS

SATA vs SAS

When it comes to interfaces for hard drives, there are only a few standards. Two of these, and the latest among them, are SATA (Serial AT Attachment) and SAS (Serial Attached SCSI). These two are the successors to PATA and SCSI respectively. The main difference between SATA and SAS is where they are meant to be used. SATA is a general purpose interface and is commonly seen in modern computers and has replaced PATA altogether. In comparison, SAS is a much rarer interface as it is only used in high-end servers where data throughput is significantly higher and the need for reliability is much greater. But the downside to SAS is its high price. Unlike SATA, which is already embedded with every motherboard available today, SAS is only available in pricier motherboards that are intended for servers.

Both these interfaces inherit commands that were used by their predecessors; SATA uses ATA commands while SAS uses SCSI commands. It is possible to tunnel SCSI commands through SATA though, as is the case with optical drives that use SCSI commands but are interface via SATA.

Another advantage of SAS is the better error reporting and recovery provided by the SCSI standard compared to SMART, which is used by SATA. This is essential with servers as it is important for drives to be replaced right away when they show signs of breaking down. This prevents unnecessary down times or loss of data. In desktops, this is not as important and not that many turn on SMART.

SAS uses higher signaling voltage levels in the transmission of commands and data. A direct consequence of this is the ability of SAS to use longer cables to connect drives. While SATA can only have cables of up to 2m, SAS drives can be attached with cables of up to 10m in length. Higher voltages are necessary for SAS in order to operate with server backplanes.

SAS is also backwards compatible with 3Gbps SATA drives. This means you can use 3Gbps SATA drives on SAS backplanes with no problems. But, you cannot use a SAS drive on a SATA backplane.

Summary:

1.SATA is for general use while SAS is for high-end server hardware
2.SATA is way cheaper than SAS
3.SATA uses ATA commands while SAS uses SCSI commands
4.SAS has better error reporting and recovery than SATA
5.SAS can use longer cables than SATA
6.SATA drives can be used in SAS backplanes but not the other way around

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