SATA

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

SATA, or Serial ATA, is a computer bus that connects a computer’s host controller to storage devices like hard drives, SSDs, and optical drives. It replaced the older Parallel ATA (PATA) standard and quickly became the main way computers store data. The SATA-IO group sets the official specs.

Why SATA was created
- Smaller, cheaper cables (seven conductors instead of many on PATA)
- Native hot swapping (you can add or remove drives without turning off the computer)
- Faster data transfer rates and optional features to improve efficiency and performance

How it works and speeds
- SATA uses a high‑speed serial link for data and shares the same basic command set as the old ATA standard for compatibility.
- Speeds have evolved: SATA I at 1.5 Gbit/s, SATA II at 3.0 Gbit/s, and SATA III at 6.0 Gbit/s. After encoding overhead, usable data rates are about 150 MB/s, 300 MB/s, and 600 MB/s respectively.
- Native Command Queuing (NCQ) started with SATA II and helps performance when multiple commands are waiting.

Compatibility and modes
- SATA is designed to be backward compatible with older ATA software, but the physical hardware is not interchangeable with PATA without adapters.
- Many motherboards offer a Legacy or IDE mode so the OS can boot without SATA drivers, but this can limit some SATA features.
- Modern operating systems support AHCI, which enables hot swapping and NCQ. If AHCI isn’t enabled, some features won’t be available.

Cables, connectors, and power
- The SATA data cable has seven conductors and is designed to be short and easy to fit in tight spaces (up to about 1 meter).
- The power connector is a 15‑pin design, supplying the drive with the required voltages.
- External connections exist as eSATA, which uses the same data protocol but a sturdier external connector and longer, shielded cables. eSATAp combines power and data in one connector, but isn’t universally available.
- For smaller devices, there are slimline variants like mSATA (used in laptops and small devices) and the newer M.2 form factor, which supports both SATA and PCIe/NVMe storage. M.2 is now the dominant small-form-factor option.
- SFF-8784 is a slim connector used for very compact 2.5-inch drives to save space.

Other technology notes
- Some SATA devices can be connected to SAS enclosures, and SATA commands can be tunneled over SAS, but not all SAS features are available to SATA drives.
- Newer interfaces like SATA Express tried to blend SATA with PCIe for higher speeds, but M.2 and NVMe became the preferred path for fast storage.
- Real-world speeds depend on the drive itself; the interface may be faster than the drive can use, especially with older hard drives.

What this means for users
- SATA provides a reliable, scalable way to connect hard drives and SSDs with easy upgrades, hot swapping, and solid performance.
- If you’re choosing storage today, you’ll likely see SATA for traditional hard drives and some SSDs, and NVMe through M.2 or PCIe for the fastest options.