SSD hard drive : Understanding the Differences Between SATA, M.2, NVMe, and PCIe
When you choose an SSD hard drive, we explain the differences between standards like SATA, M.2, NVMe and PCIe.
The SSD hard drive or the SSD standard in general has revolutionized computing in recent years. It’s not uncommon that adding an SSD can breathe new life into an old computer. But technology is advancing, and one of the criteria for that progress is speed. We want ever faster CPUs, GPUs, RAM and it is normal that the SSD hard drive has followed this trend. The SATA standard, which is the first version of SSD hard drives, is no longer sufficient for speed requirements. We now have barbaric acronyms like M.2, NVMe or PCIe. We explain all of this below.
SSD hard drive, same name, different interfaces
Me, I come from an era of computing when we still had IDE cables and good big magnetic hard drives. It was cheap, but the slowness and frequency of faults made it the biggest strain on a computer. Knowing that an SSD hard drive does not last longer since electrical interference can damage it faster.
When SATA came in, we had three successive standards, SATA 1, SATA 2, and SATA 2 that lasted for years. While how storage is designed is important, speed depends on the interface. Basically, how to read and write data the fastest in an SSD hard drive. This is where the interface comes in. Below, the respective transfer rate of the 3 SATA standards compared to PCIe which stands for PCI Express.
To transfer data, you need lanes, and the more lanes the interface can use, the faster the transfer rate. This is common sense, but it is important to understand it.
|SATA and PCIExpress transfer rates|
|SATA 1||SATA 2||SATA 3||PCIe Gen 2||PCIe Gen 3||PCIe Gen 4|
|150 Mb/s||300 Mb/s||600 Mb/s||500 Mb/s||1000 Mb/s||2000 Mb/s|
PCIe was invented to break the glass ceiling of 600 Mb/s. Even if we see that PCIe Gen 2 is limited to 500 Mb/s, we see that the third generation largely exceeds SATA and that Gen 4 (which we called PCIe 4.0 appeared in 2017) allows to have almost the quadruple of SATA. PCIe was originally used for graphics cards, but later extended to all expansion cards. It’s only a question before it hits the SSD hard drive.
NVMe and PCIe, the two go hand in hand
NVMe (Non-Volatile Memory Express) is a communications driver standard. Basically, he is the one who will tell how to manage the communication between the SSD hard drive and the CPU. Before NVMe, we had the Advanced Host Controller Interface (AHCI) which has been around since the days of magnetic hard drives. Below is the speed difference between the two standards
|Designed for||Spinning hard drive||SSD with Flash technology|
|Order queues||1||64 000|
|Can send||32 orders per queue||64,000 orders per queue|
|Latency||6 microseconds||2.8 microseconds|
|Communication type||Needs a SATA controller||Communicates directly with the CPU|
|IOPs (Input and output operation per second)||100 000||1 000 000|
We see that the NVMe is much superior. Since it communicates directly with the CPU, we have less latency and it’s much faster. And it can handle a lot more operations per second and it has more queues for orders.
But what is M.2?
M.2 is one of the SSD hard drive form factors. Basically, the kind of format and how we will install it on a motherboard. There are two types of form factors, one that is SATA compatible and one that works exclusively with PCIe.
- 2.5 format – This is the most common and the cheapest. It is inspired by traditional hard drives except it is SSD. It will nestle in one of the bays of your tower and you connect it with a SATA cable, so a transfer which will be capped at 600 Mb/s.
- mSATA – This is a format designed for notebooks and has been supplanted by M.2 which is much more compact.
- M.2 – It is also a format that is becoming widely used. Be aware that it is available in both SATA and NVMe. It has this characteristic shape of a memory stick. Today, on most shopping sites, you will only find M.2 NVMe hard drives, but don’t hesitate to read its specifications.
- The HHHL (Half Height, Half Length) – The HHHL is not really a format, but an adapter. It comes as a PCIe card and it allows you to use an M.2 SSD hard drive on older motherboards that don’t have an M.2 slot. If you want a gradual transition of your computer, this may be an option. Even though entry-level motherboards around $ 80 to $ 90 today have M.2 slots.
- U.2 – The U.2 format (pronounced Udot2) is exclusively available in NVMe and is primarily intended for servers and workstations. Not of great interest to the general public who already have M.2.
So what is the best choice of SSD hard drive?
The answer seems obvious, because the PCIe and NVMe pair seem to be the big winner if we want both compact hard drives with a transfer rate that is far superior to SATA. However, despite the fall in prices, the SATA SSD hard drive still has a bright future ahead of it, as it offers a lot on the ratio of gigabytes per dollar.
Today, you can find a good brand of 1TB SATA hard drive for around $ 50. For the same capacity in M.2, you will have to pay 80 and 100 dollars and more. So sometimes a price that is double depending on the brand. In general, we tend to recommend a hybrid configuration for today’s PCs. You put your operating system and the applications you use often on a 250 GB M.2 hard drive.
And the rest of your big files like games, videos, movies etc you put them in SATA hard drives where you can stack the terabytes without breaking the bank. Since the operating system will drive everything, putting it on a super-fast hard drive will be a real pleasure and a huge time saver.