When shopping for a new SSD or pre-built laptop, you may run into wildly different prices that don’t immediately make sense. For example, when shopping for refurbished MacBook Pros, “PCIe-based flash storage” costs more than just “Flash storage.”
What you’re seeing are SATA and PCIe SSDs. One is technologically superior, but that doesn’t mean you should always prefer it.
In this article, we’ll look at the differences between SATA and PCIe SSDs and what you need to know to make an informed decision when buying an SSD.
What Is a SATA SSD?
SATA (Serial ATA) is a type of connection interface used by SSDs to communicate data with your system. It was created back in 2003, which means it has had a lot of time to cement itself as one of the most widely-used connection types today.
SATA SSDs have better hardware compatibility. If you get a SATA SSD, it’s pretty much guaranteed to work with whatever desktop or laptop computer you have right now—even if that computer is a decade old.
SATA SSDs have worse relative performance. As of this writing, SATA 3.0 is the most prevalent form of SSD, which has a theoretical transfer speed of 6 Gb/s (750 MB/s). But due to some physical overhead that occurs when encoding the data for transfer, it actually has a practical transfer speed of 4.8 Gb/s (600 MB/s).
While 600 MB/s is pretty fast, it’s nowhere close to the transfer speeds offered by PCIe SSDs. That said, SATA SSDs are more than fast enough for casual home users—to help illustrate how fast it is, a SATA SSD can transfer an entire CD’s worth of data every second—so don’t let this be a deal-breaker.
SATA SSDs tend to be cheaper. This is probably the most important point for most home users. The truth is, the difference in price between SATA and PCIe SSDs is significant—almost as stark as the difference in price between SSDs and HDDs.
Consider the Samsung 860 EVO 500GB SATA SSD:
And compare it to the Samsung 970 EVO 500GB PCIe SSD:
While both drives are SSDs and have the same exact capacity, the SATA SSD is almost half the price of the PCIe SSD. This is true across the board: SATA SSDs are more budget friendly than PCIe SSDs.
What Is a PCIe SSD?
What is it about PCIe SSDs that make them so much more desirable and more expensive than SATA SSDs? Does it basically come down to performance? Yes, pretty much.
You can think of PCIe (Peripheral Component Interconnect Express) as a more direct data connection to the motherboard. It’s typically used with devices like graphics cards, which also need extremely fast data connections, but PCIe has proven useful for data storage drives too.
PCIe 3.0 has an effective transfer speed of 985 MB/s per lane, and since PCIe devices can support 1x, 4x, 8x, or 16x lanes, you’re looking at potential transfer speeds up to 15.76 GB/s. That’s way outside the league of SATA SSDs!
But does that mean a PCIe SSD with 16x lanes is 25-times faster than a SATA SSD? Theoretically, sure, but you won’t find a consumer-grade SSD with that many data lanes. Usually you’ll be deciding between 2x and 4x, which means a maximum transfer speed closer to 3.94 GB/s.
And even so, you’re only going to notice the difference between PCIe and SATA when transferring HUGE files that take a while. If you’re playing a video game, for example, and only want faster load speeds when starting up the game or changing maps, both PCIe SSDs and SATA SSDs will feel lightning fast.
PCIe SSDs tend to have worse battery life. If you’re just browsing the web, working in Google Docs, shooting emails, or doing something that’s purely CPU- or RAM-intensive, then you won’t notice much of a difference between SATA and PCIe SSDs (because such activities don’t involve lots of data transfer). But if you’re constantly reading and transferring data, then PCIe SSDs will use more energy and drain battery life faster.
One last note regarding AHCI vs. NVMe. If you ever have to choose between these two standards, go with NVMe. AHCI is older and was designed for HDDs and SATA, which means that a PCIe SSD using AHCI may not perform to its max potential. NVMe was designed specifically for use with PCIe, so it performs better.
What Are M.2 and U.2?
M.2 (“M dot two”) and U.2 (“U dot two”) are form factor standards that specify the shape, dimensions, and layouts of a physical device. Both the M.2 and U.2 standards are used in conjunction with both SATA and PCIe drives.
M.2 is more common by a longshot, so if you have to pick between the two and you aren’t sure which way to go, M.2 is the safer option. U.2 is mainly used for Intel 750 series SSDs and you won’t find many others that support it.
When using M.2 for a SATA SSD, performance is the exact same as using a regular SATA form factor. When using M.2 for a PCIe SSD, you’re capped at x4 lanes—which is still more than enough for a casual home user. Plus, x4 SSDs are more common than x2 SSDs and not that much more expensive, so you might as well go with that.
Note: You can buy an adapter that turns an M.2 connector into a U.2 connector or vice versa, but such adapters may not fit the physical confinements of what you’re trying to do.
PCIe vs. SATA: Which SSD Type Is Right for You?
Any way you slice it, now is a good time to buy SSD drives. If you’re on a tight budget, go with SATA. If you need maximum performance for frequent file transfers, go with PCIe.
Both are most convenient to use in the M.2 form factor, and both SATA and PCIe SSDs are demonstrably better than HDDs in terms of speed, so you really can’t go wrong either way.
Note that there are several other SSD-related terms you should know, like TRIM and SLC/MLC/TLC. You should also keep up with good SSD maintenance and be wary of these signs that your SSD is about to fail.