SATA

In short: “Serial ATA” — an older connection standard for hard drives and SSDs that runs separate data and power cables to the drive.

In more detail: SATA was developed for mechanical hard drives and, at around 600 MB/s maximum throughput, has now become a bottleneck for modern SSDs — which is why NVMe over PCIe is increasingly taking over for SSDs. For classic HDDs and cheap SSDs, however, SATA remains standard.

In Depth

SATA replaced the older, wide “Parallel ATA” (PATA/IDE) standard in the early 2000s, by transmitting data serially (over a few thin lines, one after another) instead of in parallel (over many lines at once) — paradoxically faster and more reliable than its parallel predecessor, because with parallel transmission the individual lines have to arrive exactly in sync, which became increasingly technically difficult at high speeds and longer cables. The thinner, more flexible SATA cables also improved airflow inside the case compared to PATA’s wide ribbon cables.

For mechanical HDDs, whose speed is inherently limited by rotating platters and a moving read head anyway, SATA’s bandwidth of around 600 MB/s remains completely sufficient to this day — no HDD comes anywhere near this limit. For SSDs, the picture is different: their internal flash chips could work considerably faster, but are artificially throttled by the SATA protocol and its limited command queue. That’s why the faster NVMe protocol over PCIe has become established for SSDs, while SATA remains standard for HDDs, older systems and cheap entry-level SSDs.

SATA versions and compatibility

SATA exists in several generations (SATA I at 150 MB/s, SATA II at 300 MB/s, SATA III at 600 MB/s), all backward-compatible with each other — a newer SATA III drive also works on an old SATA I port, but then only runs at its lower speed. Since SATA III (introduced around 2009), the maximum speed hasn’t increased further, since the industry’s focus since then has been on NVMe/PCIe as the faster successor path rather than another SATA generation.

eSATA as an external variant

A variant that has become rarer over time is eSATA (external SATA) — a SATA connector brought out for external drives, which (unlike USB bridges) offers native SATA speed without protocol translation. With the spread of fast USB standards (especially USB-C with high transfer rates), eSATA has lost a lot of relevance in current devices.

See also: NVMe, HDDs, M.2, External Hard Drives