NVMe vs SATA vs M.2 – Understanding Solid-state Drives
Solid-state drives and the technology surrounding them can even to this day be somewhat enigmatic. There are plenty of words and terms being used in the IT sector, and that was prior to the mainstream usage of NVME SSDs and the M.2 standard. But who can forget SATA drives, which are still to this day used, in all parts of the industry, from servers to personal computers.
The main reason these terms are often misunderstood is due to a lack of connection between what they refer to. SATA and M.2 are often used to describe a drive’s form factor, despite having more meaning. Following are explanations of what you need to know to understand NVMe, SATA and M.2.
Communication Standards – Protocols and Interfaces
Solid-state drives are not as young as people often think, the first device being created in 1991, with ideas stretching back to 1978. The technology evolved, so much so that drives were maxing out the 6 Gbit/s SATA bandwidth. Given that the interface became a bottleneck, a new one was invented, called NVM Express, or shortly, NVMe.
The battle of NVMe vs SATA is not all about speed, but also compatibility and price.
SATA – SATA or Serial ATA is an interface used to connect storage drives, mostly hard-drives and solid-state drives, as well as optical drives. Most drives using the SATA connector use the Advanced Host Controller Interface or AHCI to communicate with the rest of the computer. This was perfect for mechanical drives or hard-drives, but solid-state drives quickly maxed out the bandwidth.
Following the trend of making laptops smaller, storage also had to adapt. The 2.5-inch form factor was too large and that required a new way to connect, using PCI Express. In 2009, mSATA or micro SATA was announced, allowing SATA drives to connect using a PCIe slot. This was short-lived, because even then, the drives were maxing out the bandwidth, leading to NVM Express.
NVMe – Non-volatile Memory Host Controller Interface Specification or shortly, NVMe, is an open specification for communication via the PCIe slot. Devices making use of this standard are PCIe add-in cards, M.2 expansion cards and most notably, solid-state drives.
There are large differences in the way NVMe handles communication compared to SATA. NVMe, for example, has more command queues, 65535 compared to the one queue of AHCI. AHCI has 32 commands per queue, while NVMe has 65536 per queue. This is just the queue depth, without mentioning interrupt, data transmission and efficiency, all of which NVMe does better. This is why NVMe became the standard for SSDs, due to it being more sufficient for the way solid-state drives operate. SATA was primarily designed with mechanical drives in mind, which is why NVMe is the logical successor when it comes to drives with no moving parts.
Form Factors – M.2 vs SATA
When talking about form factors, people often use terms that describe protocols and interfaces, like SATA and NVMe. This naturally leads to confusion, because most of them describe industry standards, except M.2, which can be used to refer to size. SATA is sometimes used to determine form factors, often referring to 2.5 and 3.5 drives.
SATA 2.5 inch SSDs – These drives are among the most common drives you can purchase for laptops and desktops. Almost every desktop motherboard has a SATA port, as well as many laptops, especially in the budget range. They offer the best price to performance, as well as size.
2.5-inch drives are often mechanical, offering more size at a lower price, but also a lower performance. There have been mSATA SSDs, which are a lot smaller than regular 2.5-inch drives, but they have been superseded with NVMe M.2 drives.
This leads to the frequently asked question of NVMe vs M.2, yet the two work in unison, and not against one another.
M.2 drives – When size became the most important factor for laptops and ultrabooks, not to mention the increased need for faster drives, M.2 was created, a logical successor of mSATA. Based on the specifications of mSATA, M.2 expands on it and enables smaller drives, with more storage.
Double-sided storage chips as well as using the PCIe bus and more importantly, bandwidth, to transfer data, made the M.2 form factor a leading standard for small and fast solid-state drives. Today, PCIe 4.0 devices in theory allow for 31.5 GB/s of data transfer, for the full x16 lanes. Given that every generation of PCIe doubles the bandwidth, the theoretical limit will also be doubled with PCIe 5.0, making M.2 drives the obvious choice for high-bandwidth transfers.
The Best SSDs to Purchase – NVMe or SATA?
Depending on the use case scenario, budget and motherboard support, both NVMe and SATA drives could find a home in a personal computer.
In general, SATA drives offer the best price to performance ratio, especially when one moves their operating system to an SSD. Compared to a hard drive, the jump in speed is much larger than from a SATA SSD to an NVMe SSD.
However, when moving multiple smaller files, NVMe SSDs cannot be beaten performance-wise. Professionals often use RAID to multiply the speed of their NVMe drives, getting better performance, particularly in tasks that require moving lots of smaller files.
Regarding external drives, SATA SSDs are the most common ones, offering once more, the best price to performance. NVMe external drives do exist, but are limited to the speeds of USB, due to how enclosures work.
The question of NVMe vs SATA vs M.2 requires one to understand the difference between standards for form factors and specifications for interfaces. NVMe and SATA are interfaces, while M.2 refers to a form factor. Solid-state drives can either use NVMe or SATA standards, depending on their design and intended use.
A 2.5 inch SATA SSD is a great option for budget-oriented builds, or older laptops. NVMe M.2 SSDs, on the other hand, offer great performance at an increased price. In this case, there is no right or wrong, but rather what best fits the use case and budget range.
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