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Crucial X6 4TB Portable SSD review: Decent speed, good price to performance

Item: Crucial X6 4TB Portable SSD
Rating: 4
Author: Mike Wuerthele

Crucial's X6 4TB is small and simply designed.

Crucial X6 4TB Portable SSD

4.0 / 5

The Crucial X6 4TB Portable SSD is a cost-effective pocket-sized external SSD ideal for on-the-go storage for your Mac, with decent access speeds.

If you're carting around a MacBook Air and need some extra storage capacity, there are many options on the market that you could pick up. Main points of differentiation are speed, size, and sturdiness, and it's generally quite hard to find an external drive that can cover all three well.

The Crucial X6 is a very small external SSD that connects over USB 3.1 type C. The size allows you to easily stow it away in a bag and pull it out whenever it's required.

We've been using the 4TB variant, which Crucial rolled out in March 2021. At the time, it joined the roster alongside a 1TB and 2TB version, and the storage producer in parallel also increased the connection speed to match the larger capacity.

Key specs

Options for up to 4TB available.
USB-C 3.1 Gen 2 connectivity.
Compatible with earlier USB versions.
Sequential read speeds of up to 800MB/s claimed.
2.7 inches by 2.5 inches by 0.43 inches.
3-year warranty.

Size and design

The unassuming drive is uninspiring in design, but not everything needs to be forged by Jony Ive. It is a small square plastic enclosure, with a USB-C port on one side and the Crucial logo printed on the top panel.

It's not going to win awards with its appearance, but it's certainly adequate and what some would consider a fairly typical appearance for such an item.

The compact size of the Crucial X6 makes it highly portable.

The drive measures 69mm by 64mm (2.7 inches by 2.5 inches) and is just 11mm (0.43 inches) thick. It's also lightweight at about 40 grams (1.4 ounces).

Crucial has included a short USB Type-C to USB Type-C cable in the box, but if you carry one around anyway, it's one less thing to put into the bag. With a suitable cable or adapter, it can also connect to USB-A 3.0 or USB 2.0 ports at a corresponding drop in speed.

The Crucial X6 is also very thin (Sharpie for scale)

The company notes that the drive has shock and vibration resistance, and it is rated for drops of up to 6.5 feet.

It won't weigh down your bag, and it will easily be able to withstand being jostled around in the bag, too.

Capacity and performance

Before releasing the 4TB version, Crucial's X6 lineup was marketed as having sequential read speeds of up to 540MB/s. The 4TB model alone is rated at up to 800MB/s, all carried over a USB 3.1 Gen 2 Type-C connection, with a maximum bandwidth of 10Gbps.

AppleInsider's testing of the drive using BlackMagicDesign's Disk Speed test put the 4TB model as having read speeds of 677MB/s, while write speeds were 756MB/s. While neither are quite at the 800Mb/s, it is in the ballpark. Both speed tests are still far faster than the sub-4TB models by a long way.

AppleInsider's speed test showed the Crucial X6 4TB is quite quick, but can thermally throttle.

Over 50 sustained tests, we noticed that there was a drop in performance of around 15%. This is either a heat or cache "issue," but is acceptable for everyday use.

Compatibility and support

Unlike some other drives that include security features like onboard encryption, you're looking at a decidedly simpler device overall here. This isn't a high-security drive and is instead a block of storage you can plug in and access whenever and wherever you want.

That said, there's nothing stopping you from using various software-based tools for encryption and backup purposes. Crucial includes support for Apple's Time Machine, FileVault, BitLocker, and Windows Backup.

Naturally, it works with Macs and iPadOS devices, along with Windows, Android, and major game consoles.

In terms of support, you have a three-year warranty from the time of purchase.

Compact and capable

The Crucial X6 4TB Portable SSD is a great answer to the problem of needing extra external storage for your MacBook Pro or iPad Pro while on the move. Its small size, which is improved by reusing USB Type-C cables you may already own for other devices, makes it very easily carried around alongside your hardware.

If you're looking for something that is fully featured, offers enhanced security, and other extras, there are other drives on the market, and this wasn't ever intended to be your solution.

The included cable is short but usable, and doesn't add too much weight or size to the Crucial X6 package.

Those who want blistering speed at all times may also want to look elsewhere, as some Thunderbolt drives or external RAID enclosures can offer far faster speeds. That said, the speeds observed with the 4TB model are still more than enough for many potential users.

There are cheaper do-it-yourself solutions. You can save a couple of bucks at full retail to shell out around $360 for a 4TB SATA SSD and maybe another $25 for an external enclosure that connects over USB-C, for a total investment of just a bit less than $400. But, you're, you're going to be limited to the SATA bus speed of the DIY model at less than 550Mb/s, a few hundred below Crucial's drive, as well as lacking any of the protective elements.

The Crucial X6 4TB SSD is a no-frills drive, and it gets the job done. It does it without style, and at a good price to performance ratio.

Pros

Compact and light.
Fast connectivity over USB Type-C.
Reasonably priced.
Drop and knock protection.

Cons

Uninspiring design.
Heat throttles connectivity.
No extra encryption features.

Rating: 4 out of 5

Where to buy

The Crucial X6 4TB is available to buy at Amazon for $489.95. It can also be bought from B&H Photo for $489.95.

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10 Comments

M68000

said about 2 years ago

Thanks for this review, good to know. Love the use of the sharpie marker for size

atonaldenim

said about 2 years ago

BEWARE! Not for media pro use. Write speed plummets after drive is only 20% full! The Crucial X6 4TB drive is not suitable for anyone who wants to fill up the drive with large file transfers, say anyone working in video / audio media for example. It uses a "dynamic cache" which means the size of the write cache shrinks as the drive fills up. It's the SLC write cache that can copy files at 800MB/sec. The true QLC write speed of the drive is around 80MB/sec - slower than most old school spinning HDDs. When the drive is new and empty, the SLC write cache size is about 800GB. So the first 800GB of data you copy onto the drive will go fast. If you do a Blackmagic Disk Speed Test, that's what you'll measure, the fast SLC cache. But as soon as you've copied 800GB of data, that SLC cache almost completely disappears. Instead of 800GB of cache, it quickly drops down to like 27GB of fast write cache. When I heard the drive had an 800GB write cache, I thought that would be fine, that I could copy 800GB of data, wait a bit for the cache to empty, then copy another 800GB at the same fast speed. But no, once you've filled the drive just 20%, the write cache drops to 27GB. (It might drop even further, but I didn't have the patience to continue filling the drive past 1TB at the 80MB/s QLC crawl!) So really the 4TB X6 drive has a small 27GB write cache, plus a ~775GB bonus cache that disappears after first use. The craziest part is - the dynamic cache never grows back, after first use you'll never get that 800GB cache back again! Even if you delete all the files you've ever copied onto the drive, and the drive looks empty in your OS, the write cache stays at 27GB, it never goes back up to the full 800GB. The only way I found to get the full original write cache size back was to do a complete secure erase format of the drive writing zeros across the entire capacity. As I wanted to use this drive for video editing, I wanted to quickly fill up the whole capacity with large file transfers. Not possible with this slow-writing QLC drive. The only good uses for this drive are say Time Machine backups, where you do a large initial backup then small incremental backups afterward. It would be okay for anyone who never plans to copy any files larger than 27GB at one time. The fact that I can't get the full cache size back even after deleting all the files makes me very suspicious of this drive. I say stay away. (I formatted my drive in APFS. I actually got an error message when I first connected my drive that it had unfixable partition errors with the factory exFAT formatting, and it would only mount ready-only in MacOS, so I had to format it. It's possible that the drive might behave a little differently with other disk formats, I don't know. Personally I need it to work with APFS. And I did try running the 'trimforce' command in MacOS Mojave, I did not see a difference in the drive performance.)

Mike Wuerthele

said about 2 years ago

atonaldenim said:

BEWARE! Not for media pro use. Write speed plummets after drive is only 20% full! The Crucial X6 4TB drive is not suitable for anyone who wants to fill up the drive with large file transfers, say anyone working in video / audio media for example. It uses a "dynamic cache" which means the size of the write cache shrinks as the drive fills up. It's the SLC write cache that can copy files at 800MB/sec. The true QLC write speed of the drive is around 80MB/sec - slower than most old school spinning HDDs. When the drive is new and empty, the SLC write cache size is about 800GB. So the first 800GB of data you copy onto the drive will go fast. If you do a Blackmagic Disk Speed Test, that's what you'll measure, the fast SLC cache. But as soon as you've copied 800GB of data, that SLC cache almost completely disappears. Instead of 800GB of cache, it quickly drops down to like 27GB of fast write cache. When I heard the drive had an 800GB write cache, I thought that would be fine, that I could copy 800GB of data, wait a bit for the cache to empty, then copy another 800GB at the same fast speed. But no, once you've filled the drive just 20%, the write cache drops to 27GB. (It might drop even further, but I didn't have the patience to continue filling the drive past 1TB at the 80MB/s QLC crawl!) So really the 4TB X6 drive has a small 27GB write cache, plus a ~775GB bonus cache that disappears after first use. The craziest part is - the dynamic cache never grows back, after first use you'll never get that 800GB cache back again! Even if you delete all the files you've ever copied onto the drive, and the drive looks empty in your OS, the write cache stays at 27GB, it never goes back up to the full 800GB. The only way I found to get the full original write cache size back was to do a complete secure erase format of the drive writing zeros across the entire capacity. As I wanted to use this drive for video editing, I wanted to quickly fill up the whole capacity with large file transfers. Not possible with this slow-writing QLC drive. The only good uses for this drive are say Time Machine backups, where you do a large initial backup then small incremental backups afterward. It would be okay for anyone who never plans to copy any files larger than 27GB at one time. The fact that I can't get the full cache size back even after deleting all the files makes me very suspicious of this drive. I say stay away. (I formatted my drive in APFS. I actually got an error message when I first connected my drive that it had unfixable partition errors with the factory exFAT formatting, and it would only mount ready-only in MacOS, so I had to format it. It's possible that the drive might behave a little differently with other disk formats, I don't know. Personally I need it to work with APFS. And I did try running the 'trimforce' command in MacOS Mojave, I did not see a difference in the drive performance.)

I think you got a bad drive, and your formatting experience near the end of your post suggests that as well. We didn't have the same slowdown using APFS, and even after transferring 2TB of files at the 20% slower speed we cited in the piece, we never, ever went down to your 80 megabytes per second speed, which is sub-spinning drive speed.

And a transfer immediately after, repeating the 2TB, very obviously demonstrated a clear write cache.

I wouldn't use this drive for video editing or a scratch drive. But for a fast data repository? Sure.

flydog

said about 2 years ago

atonaldenim said:

BEWARE! Not for media pro use. Write speed plummets after drive is only 20% full! The Crucial X6 4TB drive is not suitable for anyone who wants to fill up the drive with large file transfers, say anyone working in video / audio media for example. It uses a "dynamic cache" which means the size of the write cache shrinks as the drive fills up. It's the SLC write cache that can copy files at 800MB/sec. The true QLC write speed of the drive is around 80MB/sec - slower than most old school spinning HDDs. When the drive is new and empty, the SLC write cache size is about 800GB. So the first 800GB of data you copy onto the drive will go fast. If you do a Blackmagic Disk Speed Test, that's what you'll measure, the fast SLC cache. But as soon as you've copied 800GB of data, that SLC cache almost completely disappears. Instead of 800GB of cache, it quickly drops down to like 27GB of fast write cache. When I heard the drive had an 800GB write cache, I thought that would be fine, that I could copy 800GB of data, wait a bit for the cache to empty, then copy another 800GB at the same fast speed. But no, once you've filled the drive just 20%, the write cache drops to 27GB. (It might drop even further, but I didn't have the patience to continue filling the drive past 1TB at the 80MB/s QLC crawl!) So really the 4TB X6 drive has a small 27GB write cache, plus a ~775GB bonus cache that disappears after first use. The craziest part is - the dynamic cache never grows back, after first use you'll never get that 800GB cache back again! Even if you delete all the files you've ever copied onto the drive, and the drive looks empty in your OS, the write cache stays at 27GB, it never goes back up to the full 800GB. The only way I found to get the full original write cache size back was to do a complete secure erase format of the drive writing zeros across the entire capacity. As I wanted to use this drive for video editing, I wanted to quickly fill up the whole capacity with large file transfers. Not possible with this slow-writing QLC drive. The only good uses for this drive are say Time Machine backups, where you do a large initial backup then small incremental backups afterward. It would be okay for anyone who never plans to copy any files larger than 27GB at one time. The fact that I can't get the full cache size back even after deleting all the files makes me very suspicious of this drive. I say stay away. (I formatted my drive in APFS. I actually got an error message when I first connected my drive that it had unfixable partition errors with the factory exFAT formatting, and it would only mount ready-only in MacOS, so I had to format it. It's possible that the drive might behave a little differently with other disk formats, I don't know. Personally I need it to work with APFS. And I did try running the 'trimforce' command in MacOS Mojave, I did not see a difference in the drive performance.)

https://www.baconediting.com/blog/let-your-ideas-flow-the-importance-of-paragraphs

maltz

said about 2 years ago

atonaldenim said:

BEWARE! Not for media pro use. Write speed plummets after drive is only 20% full! The Crucial X6 4TB drive is not suitable for anyone who wants to fill up the drive with large file transfers, say anyone working in video / audio media for example. It uses a "dynamic cache" which means the size of the write cache shrinks as the drive fills up. It's the SLC write cache that can copy files at 800MB/sec. The true QLC write speed of the drive is around 80MB/sec - slower than most old school spinning HDDs. When the drive is new and empty, the SLC write cache size is about 800GB. So the first 800GB of data you copy onto the drive will go fast. If you do a Blackmagic Disk Speed Test, that's what you'll measure, the fast SLC cache. But as soon as you've copied 800GB of data, that SLC cache almost completely disappears. Instead of 800GB of cache, it quickly drops down to like 27GB of fast write cache. When I heard the drive had an 800GB write cache, I thought that would be fine, that I could copy 800GB of data, wait a bit for the cache to empty, then copy another 800GB at the same fast speed. But no, once you've filled the drive just 20%, the write cache drops to 27GB. (It might drop even further, but I didn't have the patience to continue filling the drive past 1TB at the 80MB/s QLC crawl!) So really the 4TB X6 drive has a small 27GB write cache, plus a ~775GB bonus cache that disappears after first use. The craziest part is - the dynamic cache never grows back, after first use you'll never get that 800GB cache back again! Even if you delete all the files you've ever copied onto the drive, and the drive looks empty in your OS, the write cache stays at 27GB, it never goes back up to the full 800GB. The only way I found to get the full original write cache size back was to do a complete secure erase format of the drive writing zeros across the entire capacity. As I wanted to use this drive for video editing, I wanted to quickly fill up the whole capacity with large file transfers. Not possible with this slow-writing QLC drive. The only good uses for this drive are say Time Machine backups, where you do a large initial backup then small incremental backups afterward. It would be okay for anyone who never plans to copy any files larger than 27GB at one time. The fact that I can't get the full cache size back even after deleting all the files makes me very suspicious of this drive. I say stay away. (I formatted my drive in APFS. I actually got an error message when I first connected my drive that it had unfixable partition errors with the factory exFAT formatting, and it would only mount ready-only in MacOS, so I had to format it. It's possible that the drive might behave a little differently with other disk formats, I don't know. Personally I need it to work with APFS. And I did try running the 'trimforce' command in MacOS Mojave, I did not see a difference in the drive performance.)

Thanks, that's the sort of information I really look for in a storage review. Most of the rest I can get in the spec sheet. lol I do have a question, though...

"do a complete secure erase format of the drive writing zeros across the entire capacity"

For an SSD (and actually other drives) a "secure erase" has a fairly specific meaning, and it isn't "writing zeros across the entire capacity". Can you clarify the process you're talking about here? Does this device support TRIM (on Macs or any other OS) and can you do an ATA Secure Erase (or an NVMe Format)?