Understanding SSD Technology: NVMe, SATA, M.2

Data buses transfer data within a system and when NAND-based SSDs first came out, it was clear to the industry that a new bus and protocol were necessary.

• The first SSDs were relatively slow which made it convenient to use the existing SATA storage infrastructure. Even though the SATA bus has evolved to 16Gbps, nearly all commercial implementations of the SATA bus remain 6Gbps.
• PCIe 3.0’s total throughput is 16Gbps while PCIe 4.0 has double the throughput of PCIe 3.0. It offers up to 16 lanes and can transfer data up to 32,000MB/s while SATA III transfers only up to 600MB/s.

The decision to leverage an existing higher-bandwidth bus technology replaced SATA protocols with PCIe technology. PCIe storage came before NVMe by a few years but since previous solutions were bottlenecked by older data transfer protocols such as SATA and AHCI, it couldn’t be used to its full potential until recent years. NVMe was the solution for the bottlenecks and removes limitations by offering low-latency commands and 64K queues. The multiple queues allow faster data transfers because data is written to SSDs in a scattered fashion using chips and blocks rather than being written on spinning disks like hard drives.

NVMe SSDs come in a variety of form factors but they get specific depending on the use case or application.

• Personal/Client products use BGA and M.2 form factors.
• Data Center/Server applications use M.2, U.2, U.3, and EDSFF form factors.

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There are developing standards and efforts within the EDSFF (Enterprise and Data Center SSD Form Factor) which offers a dynamic range of form factors and standards that share the same protocol (NVMe), the same interface (PCIe), and use their own edge connector (SFF-TA-1002), pinout and functions (SFF-TA-1009).

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