SATA, SAS, and M.2 Connection Speeds

The performance of computer hardware standards is often advertised using theoretical maximum values measured under ideal laboratory conditions (in practice, transfer rates can be limited by device controllers, temperature, or other bottlenecks.). These figures don't necessarily reflect real-world usage speeds, but they are excellent for comparison purposes as they clearly show the differences between technological generations.

In the tables below, I provide the theoretical maximum value for each standard, rounded for readability and comparison, and always shown in bytes (specifically MB/s). I wrote about computer data transfer and storage standards, units of measurement, speeds, and their theoretical foundations here.

SATA (Serial ATA)

SATA (Serial ATA) emerged in 2003 as the successor to parallel ATA (PATA) and has become the most widespread connection standard for storage drives today. SATA's main advantage is serial data transfer, which enabled higher speeds and more efficient operation compared to the older PATA standard. IDE (Integrated Drive Electronics) was the original name, later evolved into the ATA (Advanced Technology Attachment) standard to encompass broader applications. Both SATA and PATA drives can be considered descendants of the IDE concept as they both feature integrated controller electronics, the foundation of the original IDE design.

SATA storage drives (HDDs and SSDs) are still widely used today, especially due to their cost-effectiveness. However, the performance of modern SSDs significantly exceeds the limits of SATA III, necessitating the introduction of newer technologies.

Standard	Interface Speed	Data Rate (MB/s)	Common Use
PATA (IDE - UDMA/133)	133 Mbps	~16.6 MB/s	Older HDDs
SATA I	1.5 Gbps	150 MB/s	Older HDDs, early SSDs
SATA II	3 Gbps	300 MB/s	HDDs, entry-level SSDs
SATA III	6 Gbps	600 MB/s	Modern SSDs, HDDs

SAS (Serial Attached SCSI)

SAS (Serial Attached SCSI) is a high-performance connection standard primarily used in enterprise environments. Like SATA, it uses serial data transfer, but it is much more robust and reliable, making it ideal for servers and data centers. SAS controllers and backplanes are generally compatible with SATA drives (allowing SATA drives to be plugged into SAS systems), but SATA controllers cannot handle SAS drives. SAS storage devices are more expensive but are well-suited for high-load environments where reliability and performance are critical.

Standard	Release Year	Interface Speed (Gbps)	Data Rate (MB/s)
SAS-1.0	2004	3 Gbps	300 MB/s
SAS-2.0	2009	6 Gbps	600 MB/s
SAS-3.0	2013	12 Gbps	1,200 MB/s
SAS-4.0	2017	22.5 Gbps (effectively)	~2,400 MB/s

*Note: SAS speeds per lane are listed. SAS interfaces can use multiple lanes.*

M.2 Form Factor (SATA, NVMe)

M.2 is not an interface standard itself, but rather a form factor primarily used for SSDs. The M.2 connector enables the use of small, high-performance storage devices and supports multiple interfaces, most notably SATA and NVMe (Non-Volatile Memory Express), which typically uses the PCIe bus.

M.2 Type	Underlying Interface	Theoretical Speed (MB/s)
M.2 SATA	SATA III	600 MB/s
M.2 NVMe (PCIe 3.0 x4)	PCIe 3.0 x4	~3,940 MB/s
M.2 NVMe (PCIe 4.0 x4)	PCIe 4.0 x4	~7,880 MB/s
M.2 NVMe (PCIe 5.0 x4)	PCIe 5.0 x4	~15,750 MB/s

*Note: The speeds listed for M.2 NVMe drives are based on the theoretical maximum bandwidth of the PCIe interface they use (typically 4 lanes). Actual drive performance varies.*

Summary

• SATA: The most cost-effective solution for home and office environments where maximum speed is not the primary concern (suitable for HDDs and mainstream SSDs).
• SAS: Designed for high-performance servers and data centers requiring high reliability, robustness, and fast data transfer for demanding workloads.
• M.2 (NVMe/PCIe): Used in modern computers, gaming rigs, and professional workstations where maximum storage speed is needed, leveraging the PCIe bus via the NVMe protocol.