The road to Bus Interface of HHD, from ATA to SAS

2020-01-18 17:09:13

Hard disk drives are accessed over one of a number of bus types, including parallel ATA (PATA, also called IDE or EIDE; ), Serial ATA (SATA), SCSI and Serial Attached SCSI (SAS). There are also some other interface that hard disk drives used, but these are four most important bus types.

Among these four, ATA and SATA can be as a twin, while SCSI and SAS are another twin. They have a common point, which is parallel and serial. ATA uses a way of parallel, but SATA uses serial. And SCSI uses a way of parallel, but SAS uses serial.

Let me introduce more details of each.


1. ATA

Parallel ATA (Parallel Advanced Technology Attachment or PATA) is a standard for connecting hard drives into computer systems. As its name implies, PATA is based on parallel signaling technology. Parallel ATA dates back to the 1980s. Integrated Drive Electronics ( IDE ) drives operate according to this standard.



ATA interface



Serial ATA (Serial Advanced Technology Attachment or SATA) is a standard for connecting and transferring data from hard disk drives (HDDs) to computer systems. As its name implies, SATA is based on serial signaling technology, unlike Integrated Drive Electronics (IDE) hard drives that use parallel signaling.





The fastest SATA now is SATA 3.0, which supports speed up to 6Gb/s. While the original SATA 1.0 has the speed up to 1.5Gb/s.

The bandwidth of SATA Generation:

•SATA 1.0 1.5Gb/s

•SATA 2.0 3Gb/s

•SATA 3.0 6Gb/s



SCSI (pronounced SKUH-zee and sometimes colloquially known as "scuzzy"), the Small Computer System Interface, is a set of American National Standards Institute (ANSI) standard electronic interfaces that allow personal computers (PCs) to communicate with peripheral hardware such as disk drives, tape drives, CD-ROM drives, printers and scanners faster and more flexibly than previous parallel data transfer interfaces.





4. SAS

Serial-attached SCSI (SAS) is a method used in accessing computer peripheral devices that employs a serial (one bit at a time) means of digital data transfer over thin cables. Compared to other bus protocol, SAS is most widely used in storage field. Look at the below figure, which shows the history of SAS’s development.


The bandwidth of SAS Generation:

•SAS 1.0 3.0Gb/s

•SAS 2.0 6.0Gb/s

•SAS 3.0 12.0Gb/s

•SAS 4.0 24.0Gb/s