SATA
Serial ATA (SATA) is a computer bus interface that connects storage devices like hard disk drives (HDDs), solid-state drives (SSDs), and optical drives to the motherboard in a computer. Its main job is to transfer data between these storage devices and the rest of the computer.
SATA was created to replace the older Parallel ATA (PATA) interface. The "Serial" in its name means data is sent bit by bit over a single pair of wires, unlike PATA which sent many bits at once over multiple wires.
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Overview
SATA offered several benefits over PATA, including faster data transfer, simpler and thinner cables (which improve airflow inside the computer), and support for features like hot-swapping (connecting or disconnecting devices while the computer is on).
Because it was so widely adopted, SATA has been the standard interface for most internal storage in desktops, laptops, and servers for over a decade. While faster interfaces like NVMe are now common for high-performance SSDs, SATA is still widely used for larger capacity HDDs and many mainstream SSDs.
History and Evolution
SATA was first introduced in 2003, replacing PATA. Since then, the standard has evolved through several generations, primarily increasing the maximum data transfer throughput:
- SATA 1.0 (SATA I): Max theoretical throughput of 1.5 Gbit/s (approx. 150 MB/s).
- SATA 2.0 (SATA II): Max theoretical throughput of 3 Gbit/s (approx. 300 MB/s).
- SATA 3.0 (SATA III): Max theoretical throughput of 6 Gbit/s (approx. 600 MB/s). This is the most common version in modern computers.
- SATA 3.2 (SATA Express): An attempt to use PCIe to boost speed (up to 16 Gbit/s), but it didn't become widely adopted due to the rise of direct NVMe over PCIe.
Each new version of SATA is backward compatible with older versions, though the speed will be limited by the slowest device or port.
Advantages over PATA
SATA brought significant improvements when it replaced PATA:
- Higher Throughput: Faster, with subsequent versions increasing the speed.
- Thinner, More Flexible Cables: SATA uses thin, seven-pin data cables, improving airflow and making installation easier than PATA's wide ribbon cables.
- Simpler Connectors: Smaller and easier to connect.
- Hot-Swapping Support: SATA supports hot-swapping (connecting or disconnecting devices while the computer is running).
- Lower Voltage: Uses lower signaling voltages, reducing power consumption.
Comparison to NVMe
While SATA was a big upgrade from PATA, it was designed when HDDs were the main storage. Its protocol and speed limits (peaking at 600 MB/s) became a bottleneck for SSDs, which are much faster. NVMe is a newer interface designed specifically for the speed of flash memory.
NVMe connects SSDs directly to the CPU via PCIe lanes, offering significantly higher Throughput (thousands of MB/s) and lower Latency compared to SATA. Therefore, for maximum SSD performance, NVMe is preferred over SATA.
Connectors and Form Factors
SATA uses distinctive L-shaped connectors:
- SATA Data Connector: A 7-pin L-shaped connector for data transfer.
- SATA Power Connector: A 15-pin L-shaped connector to supply power to the drive. It replaced the older 4-pin Molex connector.
SATA drives come in standard form factors:
- 2.5-inch: Standard size for laptops and common for most SSDs.
- 3.5-inch: Standard size for desktop HDDs.
- Optical Drive Form Factors: CD, DVD, and Blu-ray drives typically use SATA.
- mSATA: A smaller form factor using the SATA protocol, typically for small SSDs (largely replaced by M.2).
- M.2: A compact form factor used for both SATA and NVMe SSDs (check specifications to know which protocol it uses).
