SATA and eSATA are two bus interfaces used for data transfer in computers. In this article, I present a comparison between the two, that highlights the main points of difference between these technologies.
Sata cable
When it comes to evaluating the performance of a computer, besides processing power, what matters is the data transfer rates that it can achieve. One of the main factors on which the data transfer rate is dependent is the kind of computer bus interface used to form the link between the bus adapters and storage devices such as the hard drives or the optical drives.

SATA and eSATA are two of the most popularly used bus interfaces. In the following lines, we shall find out what they are, and compare them on various counts.

What are eSATA and SATA?

SATA stands for 'Serial Advanced Technology Attachment', which is the most widely used computer bus technology in the world today. SATA is confined to act as the default computer bus for internal hard drives and optical drives.

It was developed to update the ATA technology and provide superior bandwidth and data transfer speeds. This was achieved through the usage of high speed serial cables. Compared to PATA (Parallel Advanced Technology Attachment), SATA is much faster and comes with a lesser bulk of cables. Today the SATA interface is so well established as a part of essential technology, that the SATA host adapter is inbuilt in almost all the computer motherboards.

eSATA is actually an extension of the SATA technology, used for connecting external devices. The 'e' in eSATA stands for 'external'. It was designed so that the advantage of high data transfer rate of SATA, could be harnessed to make data exchange from devices like external hard drives faster. ESATA in fact, is a faster alternative to USB and FireWire based devices.

eSATA Vs. SATA Comparison

Let us have a look at the major differences between SATA and eSATA according to the various technical specifications like the type of cable, connectors, speed, and performance.

eSATA has identical protocol and signaling mechanisms to SATA. This enables the conversion of an internal SATA hard drive into an eSATA hard drive, with only a small amount of modifications. However, the fact that eSATA is meant to be used as an external device connector, necessitated that a different type of connector be created for it.

The eSATA connector is essentially a shielded version of the standard SATA 1.0a connector. The depth of insertion of this connector is increased to be 6.6 mm, instead of the 5mm, that is standard for SATA connectors. This modification has been made to prevent damage due to electric discharge. Also, these external connectors are so designed that they can last for at least five thousand insertions and removals.

Another difference between eSATA and SATA, is the particular type and length of the cable used for each. Both cables have extra shielding, to prevent electromagnetic interference, however, the length of the cable used for eSATA is 2 meters as opposed to the 1 meter of SATA.

The first generation SATA supported speeds of 1.5Gbit/s (150 MB/s). However, over the years several revisions have been made to this technology, and it now supports the following speeds: 3.0, 6.0 and 16 Gbit/s.

All the SATA transfer speeds are supported by eSATA up to 6Gbit/s(600MB/s); though, some of them are limited to 3Gbit/s (300 MB/s) or less. Note however that even at 300MB/s, eSATA is still much faster than other external connectivity interfaces, including 1394a/FireWire 400(50 MB/s) and USB 2.0 (60MB/s).

If a performance comparison is made between eSATA and SATA according to speed of data transfer, then SATA is ahead. However, a direct comparison to determine the overall performance cannot be made as the two technologies serve different purposes. When it comes to usage as an internal computer interface bus with hard drives, SATA is unbeatable while, in terms of data transfer from external devices, eSATA is the clear winner as SATA does not have that capability.

Both technologies have a number of similar features, and the differences between them arise from the fact that they are meant for different purposes. eSATA has been developed as an alternative to USB and FireWire. eSATA external hard drives are especially in demand due to the high data transfer rates that they offer as compared to other technologies. However, a major roadblock for its development is the absence of eSATA ports on most desktop and laptop computers. In the future, as this technology finds more widespread uses, eSATA ports will probably become more common. As for SATA, owing to its speed advantage, it is certainly capable of being the mainstay as the default internal bus interface for years to come.