Why NVMe rather than SATA

Intro

As technology evolves, the need for high speed, high-capacity storage is only becoming more prevalent. While SATA based drives use to be the main go-to data storage solutions, nowadays they have largely been supplanted and replaced by newer NVMe drives.  In this article, we’ll take a closer look at NVMe and why it’s become the gold-standard and future for most storage solutions.

AHCI Protocol vs. NVMe: SATA Limitations for SSDs

While both are flash memory-based storage devices, the actual interface between NVMe (Non-Volatile Memory Express) and SATA solid state drives (SSD) differ significantly. SATA SSDs rely on the AHCI (Advanced Host Controller Interface) protocol. This protocol operates as an interface between the SATA controller and the storage devices connected to it. Originally, AHCI was designed for hard drives and later adapted to SSDs when they first were introduced. While this worked well for early model SSDs, as they continued to become more advanced, the limitations of AHCI became more and more apparent.

For example, ACHI only has a single command queue and is limited in its overall queue depth. This restricts the SSD’s ability in handling multiple commands simultaneously. As a consequence, this can lead to increased latency during SSD operations.

Another issue is the SATA interface itself. The current version of the interface is SATA 3 which has a bandwidth cap of 6Gbs. Like the AHCI protocol, this speed cap was fine for traditional hard drives as due to their spinning platters, they were physically incapable of maxing out the bandwidth provided to them. However, with the advent of SSDs and their lack of moving parts, it quickly became apparent that this interface was now acting as a bottleneck and preventing maximum performance.

Benefits of NVMe SSDs

This all changed with the introduction of NVMe. Unlike the SATA interface, NVMe can communicate directly with the system CPU via the PCIe (Peripheral Component Interconnect Interface). Overall, this reduces total latency and overhead. In turn, this results in much higher performance than SATA is capable of, with it being able to provide bandwidth in the thousands of MBs opposed to the hundreds that SATA can support. Additionally, as the PCIe interface continues to update, this increases the total data transfer rate it’s able to support.

PCIe Interface and SSD Performance

Version	Transfer Performance x1	Total Transfer Performance x16
PCIe 1.0	250 MB/s	4 GB/s
PCIe 2.0	500 MB/s	8 GB/s
PCIe 3.0	~1 GB/s	~16 GB/s
PCIe 4.0	~2 GB/s	~32 GB/s
PCIe 5.0	~4 GB/s	~64 GB/s

NVMe Command Queue Advantages

Another added advantage of NVMe is the increase in command queue and the number of commands that can be sent per queue. As previously mentioned, SATA is limited to a single command queue. NVMe on the other hand can support up to 64K queues and is able to send 64K commands per queue.

Due to their massive increase in performance, NVMes has become the go-to storage solution for a variety of different applications. This can range from data center usage which requires high-capacity, sustained and continuous performance to projects that are system intensive and require ultra-fast speeds. NVMe is particularly well suited for AI and ML Workloads. These demanding applications require high-speed, high-density storage solutions. During their initial phases, most AI algorithms will need to process massive datasets of both structured and unstructured data. By using NVMe, one is able to provide storage that is able provide the fast access speeds which reduces the total time required for this stage.

Future of Storage: NVMe SSDs

Why choose NVMe over SATA? By now, the answer should be obvious. With NVMes ability to provide high-speed, low-latency storage, and reduce total overhead it’s obvious which storage option should be chosen for projects looking for the most fastest solution possible.