Here’s whether USB bottlenecks external drives:
The USB port bottlenecks an external storage drive when the drive is capable of speeds that the port can’t handle.
In data transfers, the slowest component dictates the speeds, so you want USB ports that can keep up.
Fortunately, the most common USB port can keep up with the most common external drives.
So if you want to learn all about how USB bottlenecks exactly external drives, then this article is for you.
Let’s jump right in!
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Does a USB Bottleneck External Drives?
USB definitely can bottleneck your external drive.
It depends entirely on the setup and the different components involved.
I’ll go through all of it, but let’s start with one of the more common setups.
SSDs really have taken over, and they’re probably the most common type of disk drive available right now.
Additionally, USB 3 is probably the most common USB port on consumer electronics.
So, if you have an external SSD connected through a USB 3 slot, the USB and SSD run at close to the same speed.
Regardless of which one is slower, you won’t see an overwhelming bottleneck because they’re close to each other in performance.
I will explain all of this in full detail.
I wanted to get the short answer out there first.
But, if that situation doesn’t describe your setup, then the USB might not be a bottleneck.
It depends, so it’s best if we go through all of the drives and USB connections.
After that, you’ll be able to determine how well your setup can function.
What Are the Different USB Types?
There are actually a lot of different USB types.
To keep things simple, I’m going to focus on the most common.
On top of that, I’m going to lump a few categories together.
So, you’ll see USB 2.0, USB 3.0, and USB-C sections below.
Really, there are variations among these USB categories, but those differences don’t matter too much.
So, I’ll call all USB 3 variations USB 3.0, even if that isn’t technically right.
It makes things easier, and I’m doing the same with USB 2.0 and USB-C.
#1 USB 2.0
USB 2.0 is pretty old at this point.
It first launched in 2000.
In computer terms, that’s at least a million years ago.
But more seriously, USB 2.0 was the gold standard for a long time.
Over the last decade (a little more actually), it has slowly been replaced by USB 3 (and its upgrades).
So, today, a lot of devices don’t have USB 2.0 at all.
That said, some computers, especially budget computers, still do.
Here’s the thing with USB 2.0.
Because of its age, it’s not very fast.
The maximum data speed for this version of USB is 480 Mbps.
I’ll get into the specifics of data rates a little later, but this is a slow rate.
SSD drives can process data much faster than this.
But, for HDD drives (which are still popular for external storage), this is fast enough.
Those drives usually run a lot slower, and even a USB 2.0 isn’t a bottleneck.
USB 3.0 launched in 2008, and it has seen several upgrades since.
It was designed to allow more power to flow through the connection (allowing USB 3.0 to power more demanding devices).
Most of all, it aimed to dramatically improve data transfer rates.
The current version in use is USB 3.2, and it hits data rates up to 5 Gbps.
This is much faster than any HDD, so it isn’t creating bottlenecks there.
As for SSDs, their performance can range wildly, so it really depends on the hardware you are using.
Still, typical SSD speeds clock in at rates lower than this, which is why I said USB 3.0 isn’t a bottleneck in the opening.
USB-C is fast becoming the new standard.
It’s the standard charging and transfer cable for Android phones.
The EU recently demanded that Apple products start using USB-C.
On top of that, it’s a lot faster and better than USB 3.0.
How much better?
For now, USB-C can handle data rates of 10 Gbps, and future improvements on the technology might raise that number before anything replaces USB-C.
High-end external SSDs don’t quite get up to 10 Gbps right now, so with USB-C, you’re in the clear.
In the future, that might not be true, but for now, USB-C isn’t bottlenecking your data transfers.
What About Drive Types?
We’ve covered half of the equation so far.
Now, it’s important to get into the drives themselves.
For the most part, storage drives come in three forms:
NVMe drives aren’t commonly used for external storage.
I’m still going to explain NVMe drives, but most likely, your external drive doesn’t use this technology, and it won’t really be a factor for you.
The short version is that SSDs are much faster than HDDs, but I’m going to go into greater detail and give you some raw numbers to back that up.
An HDD is a hard disk drive.
This is a drive that has a spinning platter that reads and writes information.
We don’t really need to get into the mechanics of how drives store data.
What matters is that the rotation limits how fast the hard drive can process information.
Good HDDs will rotate at about 7200 RPM (although you can find drives with different rotation speeds).
This very fast level of rotation still only provides data processing at rates around 150 Mbps.
That’s considerably slower than any of the USB types, so with an external HDD, you’re just not worried about the USB port.
It’s not a problem.
SSDs, or solid-state drives, are a different matter.
They don’t have moving parts, and that means they don’t have the same limitations as HDDs.
Because of that, SSD speeds get a lot faster, and trying to pin down the speed of your SSD isn’t always easy.
Even a few years ago, a fast SSD would run at around 500 Mbps.
That would be well below USB 3.0 limitations and not a problem.
But today, you can get SSDs that are considerably faster.
For instance, SanDisk’s Extreme Portable external SSD runs at 1050 MBps.
The difference between the capital and lower-case “b” in this instance is meaningful (and explained more in the next section).
This means that the drive can process data at a rate of over 8 Gbps.
That’s faster than USB 3.2, but it’s still slower than the peak for USB-C.
That said, I’m choosing an extreme example.
The vast majority of external SSDs are going to be slower, usually running between 800 Mbps and 8.4 Gbps.
For the most part, that all sits in the range of USB 3.0.
Yes, the faster of what I’m listing will be bottlenecked by the USB, but not by very much.
More importantly, engineers understand these limitations.
Most external drives that are much faster than USB 3.0 are designed to work with USB-C instead.
So, if you follow manufacturer recommendations, you can avoid severe bottlenecks.
Ultimately, this advice is going to prove dated.
SSD drive speeds are expanding much faster than USB 3.0, so there will come a time when it is a definite bottleneck.
What Do Data Speeds Really Mean?
I’m trying to use raw data to help you see the differences in performance across these technology types.
But, the numbers don’t mean much without a deeper explanation.
So, let’s go over what these numbers really mean. Then, I’ll give you some examples for more context.
For starters, there are two ways to measure data: bits and bytes.
They’re actually related.
The most basic unit of data storage on a digital device is called a bit.
It holds a very small amount of information.
This sentence takes up more than one bit.
So, you need a lot of bits to really make data meaningful.
To help with that, bits are arranged into bytes.
A byte consists of eight bits.
That’s a seemingly random arrangement, but that’s how it is.
So, any measurement in bytes is eight times bigger than the same number expressing bits.
Bear with me. This is where things get a little pedantic.
The standard to abbreviate a byte is a capital B.
The standard for a bit is lower case.
So, when you see 1 MBps vs 1 Mbps, the first measurement is 8 times bigger than the second.
Speaking of that, what do those other letters mean?
The first letter is a prefix telling you how many bits or bytes there are. These follow metric conventions, so you’ll see “M” for mega, “G” for Giga, and so on.
In consumer electronics, you’ll mostly deal with mega and Giga.
Mega means 1 million, and Giga means 1 billion.
So, there are 1,000 Megabytes (GB) in a single Gigabyte (GB).
This relationship holds true for bits as well.
The second letter in the measurement is telling you if it’s bits or bytes (based on whether or not the “b” is capitalized).
The last two letters are consistent.
The “ps” just stands for “per second.”
Sometimes, you’ll see a data rate written as Mb/s instead.
It means the exact same thing.
What Are Examples of Data Sizes?
That was very technical, so let’s get into some examples that make sense.
The easiest way to compare data sizes is with things people actually store.
A nice, high-quality photo usually takes up a number of MBs.
Now, this will depend on the size of the photo and the pixel count, and we don’t need to get into that.
But good pictures are in the MB range.
A high-definition movie is going to take up GBs of space (usually less than 10).
Again, it depends on how long the movie is and how high the definition is, but that’s your ballpark.
So, an SSD connected through USB 3.0 can transfer a whole high-definition movie in a matter of seconds.
In fact, that setup could transfer the entire Marvel Cinematic Universe in a few minutes.
With that perspective, you can see that bottlenecks on USB drives aren’t always a problem.
If you can transfer movies in seconds, the drive is definitely fast enough for you to watch them in real-time.