Difference between SAS and SATA

Key Difference: SAS and SATA, both define the types of data storage protocol standard that have been designed to transfer the data between the host system and mass storage devices. SATA stands for Serial Advanced Technology Attachment. It refers to the next generation computer bus interface that has evolved from the parallel interface ATA. SAS, or Serial Attached SCSI, is a serial communication protocol for direct attached devices. These are generally faster and historically more expensive interfaces than compared to SATA. SAS drives are regarded to be ideal for servers, whereas SATA drives are preferred for desktop computers.

SAS can be defined as a successor to the parallel SCSI interface technology. Basically, it is a computer bus technology that has been developed for the transfer of data to and from devices like hard drives, CD-ROM drives, etc. It uses the advantages of SCSI functionality and has been built on the already existing capabilities of enterprise storage connection. The features include –

Drive addressability of up to 16,256 devices per port.
A reliable point-to-point serial connection at speeds of up to 3G bps (375 MB/s).

It has been very effective in replacing the old Parallel SCSI bus technology. The SAS protocol is developed and maintained by the T10 committee. The protocol that defines the mechanism of SAS, comprises of three transport protocols:

Serial SCSI Protocol (SSP) – This protocol supports SAS disk drives.
Serial ATA Tunneling Protocol (STP) - This protocol supports SATA disks.
Serial Management Protocol (SMP) – This protocol manages SAS Expanders.

SATA stands for Serial Advanced Technology Attachment. It refers to the next generation computer bus interface that has evolved from the parallel interface ATA. SATA can be viewed as a serialized enhancement and replacement to parallel IDE. Transfer rates for Serial ATA start at 150MB/s. SATA is the predominant disk interface technology that is used in the following entities:

Desktop PCs
Entry-level servers
Entry-level networked storage systems

Comparison between SAS and SATA:

	SAS	SATA
Full form	Serial Attached SCSI (Small Computer System Interface)	Serial Advanced Technology Attachment
Definition	SAS can be defined as a successor to the parallel SCSI interface technology. It is basically a computer bus technology that has been developed for the transfer of data to and from devices like hard drives, CD-ROM drives, etc.	It refers to the next generation computer bus interface that has evolved from the parallel interface ATA. SATA can be viewed as a serialized enhancement and replacement to parallel IDE.
Identification	These devices are recognized by the world wide name.	These devices are recognized by their port number connected to either host bust adapter or by their universally unique identifier.
Objective	To work for mission critical enterprise applications.	To work as a general purpose interface common in the consumer market.
Mode of transfer	Full duplex	Half duplex
Cable Length	Support cables up to 8 meters long.	Maximum cable length is 1 meter.
Performance	SAS drives have higher performance than desktop SATA drives.	Enterprise SATA drives may perform better than desktop SATA drives.
Signaling Voltages	Higher (800–1600 mV TX, 275–1600 mV RX)	Comparatively low (400–600 mV TX, 325–600 mV RX)
Advantages	Higher bandwidth 300MB/s point-to-point links. Allows the grouping of multiple links for wide links in multiples of 300MB/s. Allows the choice of SAS and/or SATA drives in the same infrastructure. Traditional SCSI software and middleware. Smaller connectors allow for small form factor hard disk drives. Simplified signal routing and thinner cabling	Parallel ATA technology is approaching its physical transfer rate limit. SATA has smaller cables and a smaller pin count. SATA offers a growth path to match the increasing data rates of disk drives. Point-to-point data transfer starts at 1.5Gb/s.
Disadvantages	Higher cost per GB System complexity with active components Much lower capacity drives	Limited external support Shorter cable length Expandability (limited to controller’s port count)