Is It Worth Buying External NVMe Drives Over Regular SSDs?

NVME SSDs are the fastest mainstream type of storage you can install in your computer, and there are plenty of external enclosure options you can buy to use with these drives, but are external SATA SSDs actually more sensible to buy?

Clearing Up the Jargon

This discussion has quite a few acronyms and technical terms in the mix, so it’s probably a good idea to quickly explain the most important ones:

• NVMe: NonVolatile Memory articulate is a communication protocol meant for SSDs (Solid State Drives) specifically. It takes advantage of the high-performance possible with SSD storage. NVMe drives generally convey over PCIe (Peripheral Component Interconnect articulate) which is why it’s often labeled PCIe NVMe.
• SATA: Serial Advanced Technology Attachment: This is a common protocol with its own specialized connector originally designed to mechanical hard drives, to exchange the older PATA (Parallel Advanced Technology Attachment) standard. For obvious reasons, at first commercial desktop SSDs were compatible with SATA so that they could be drop-in replacements for mechanical drives. Today, you can also get SSDs that use the SATA protocol, but connect to the same M.2 slot that NVMe drives do. So it’s important to know what protocols the drive and slot maintain!
• Bits and Bytes: A bit or binary digit is either a one or a zero. It’s the smallest unit of data possible in a binary computer. A byte is conventionally eight bits in length. So eight Megabits are equal to roughly eight Megabytes. This is important because the speed of connections is generally measured in bits per second, but most people are more familiar with measuring data as storage space in bytes. Simply divide the measurement in bits by eight to get the estimated number in bytes.
• USB and Thunderbolt: USB and Thunderbolt are two of the most popular external peripheral connection standards, with USB being virtually ubiquitous and Thunderbolt gaining a strong foothold in mid-range to high-end computers. There are multiple versions of each standard with different speeds. Any external drive almost certainly uses one or both of these connection standards.

If you got all that, you’re more than prepared to comprehend what type of external SSD makes the most sense to buy.

NVMe vs SATA SSDs

NVMe SSDs generally use the M.2 slot type to connect to a computer. SATA SSDs use a SATA cable. The actual SSD chips in each type of drive use the same fundamental technology, but the protocols send and acquire data differently.

The end result of their under the hood differences is that SATA III (the latest version) has a maximum theoretical bandwidth of 6Gbps (Gigabits per second) although thanks to some quirks of how it encodes data, the fastest and SSD can transfer data is just short of 5Gbps, or 600 MB/s (Megabytes Per Second).

For NVMe drives, it all depends on the drive’s memory technology and the PCIe connection speed. Here are some relevant examples:

• NVMe PCIe Gen 3×4: This is a PCIe 3.0 interface with four “lanes” for data. These drives can read at up to 3,500 MB/s and write at up to 2,700 MB/s. That’s almost 30Gbps in read speed performance!
• NVMe PCIe Gen 4×4: Here the theoretical limit is 7,880 MB/s, and it’s typical for good quality 4×4 drives to read and write at speeds over 7,000 MB/s.

Faster speeds are already here, which can be achieved by adding more lanes. Although this usually requires SSDs on a PCIe card, rather than an M.2 connection. The latest Gen 5×4 drives using M.2 will happily hit 10,000 MB/s.

Clearly, NVMe is superior to SATA in every way that matters, but that performance comes at a cost. Although Gen 3 NVMe drives have started hitting reasonable price points, they’re still much more expensive than SATA SSDs of equivalent capacity.

This is the crucial point when it comes to external drives, because no matter how fast the drive itself is, you can’t go any faster than the connection type. Which brings use to the next issue.

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How Fast Are USB and Thunderbolt?

So you’re connecting to an SSD via USB or Thunderbolt, which means that the SSD protocol is being converted in most cases, (e.g. from SATA to USB) which introduces some level of overhead. Then, the maximum throughput sets a hard limit on the top speed possible. Here are the pertinent limits:

• USB 3.0: USB 3 starts at around 5Gbps. which is around 600 MB/s. As we advance up the USB specs, that speed doubles to 10, 20, and, with USB 4, 40 Gbps. So, the very latest USB standard has a theoretical upper limit of roughly 5,000 Megabytes per second.
• Thunderbolt 3 and 4: admire USB 4, both Thunderbolt 3 and 4 have an upper limit of 40Gbps.

At the time of writing, we are about to get 80 Gbps versions of both USB and Thunderbolt, pushing that theoretical upper limit to around 10 GB/s. However, it will be some time before even 20Gbps or 40Gbps connections are commonplace on most computers.

Picking the Optimal External SSD

If you’re buying a pre-made external SSD, then the manufacturer has likely already paired the correct interface to match the performance of the SSD itself, although of course you should double-check this using what you’ve learned so far.

However, if you’re rolling your own external SSD using an enclosure and an off-the-shelf internal drive, it’s crucial that you don’t waste money buying a drive that’s far faster than a given enclosure’s rated speed.

Likewise, if you already have an SSD you want to repurpose, don’t buy an enclosure that will bottleneck it. It’s fine, even sensible, to buy an enclosure that exceeds the speed the drive can reach, but not the other way around.

Also, what connections does your computer actually offer? If you’re not in any rush to upgrade your computer, then it doesn’t matter what external SSD you connect to, if the computer’s own speed limit will apply. If you only have 5Gbps USB 3 ports, that’s how fast the SSD can go at most.

Finally, think carefully about how much speed you actually need. 600 MB/s over SATA is still phenomenally fast. If you’re using the external SSD for storage or other applications that don’t need speeds faster than 600 MB/s, it makes more sense to either save money or divert the price difference compared to NVMe towards extra capacity.

Getting to the Bottom Line

That’s a lot of information for something as simple as an external drive, but the fact is that SSDs are not cheap, so let’s boil it down to the simplest steps:

• Check the speed of the drive in its specifications.
• Check if the connection standard of the drive is less than the drive’s ability.
• If you’re making your own external drive, select an enclosure that meets or exceeds the drive’s capabilities.
• Ensure the computer you’ll be using the drive with has ports fast enough to do the external drive justice.

It’s definitely worth investing in an external NVMe drive if you allow it to reach its maximum speed, but if you aren’t giving it room to stretch its legs, you’re better off saving your money and buying a slower NVMe drive, or even a large capacity SATA SSD for the same price.