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Designed for the most demanding needs of photographers and videographers.
The fastest, toughest, and most compatible portable SSD ever with speeds up to 2800MB/s.

4TB Crucial X6 USB-C SSD

BH Photo loaned MPG the about $229 4TB Crucial X6 Portable SSD CT4000X6SSD9 for testing. Direct-connect to the 2022 MacBook Pro M2 Max via Thunderbolt/USB 4 port. Tests via diglloydTools DiskTester.

Consult with Lloyd to design a storage and/or backup system and/or high performance workflow.

Crucial X6 Portable SSD

MPG tested the 4TB Samsung T7 Shield SSD and 4TB SanDisk Extreme PRO V2 just prior to the Crucial X6, with excellent results.

With the low pricing of the Crucial X6, MPG expected to see miserable write performance (as seen with the 2TB Samsung T7 back in 2021), but like the 4TB Samsung T7 Shield, the Crucial X6 shows no sign of the 2-tier-flash write slowdown—the X6 runs at full speed for its entire capacity. But with real-world usage, its performance plunged soon after running the benchmarks; see Real World results.

Perhaps 2021 was the year of 2-tier flash, conditions changed, and every SSD vendor upgraded its flash silently? Reader Abe H comments that his 2021 Crucial X6 also had the write-speed plunge characteristic of 2-tier flash, just like the Samsung T7 that MPG tested in 2021.

Reliability, build

Field usage over time is required to establish long-term reliability, but the X6 looks well-built and unlikely to have issues.

Exceptionally compact and lightweight, notable smaller than its Samsung and SanDisk competitors, the X6 easily slips into even a tight pocket.


Crucial uses MB = 1024 * 1024. Test results further below are in MiB (1024 * 1024), a factor of 1.048576X difference. Even so, it easily outperforms the specifications.

The Crucial X6 comes with one very short USB-C to USB-C cable, but inexpensive USB-A cables are available for connecting to traditional USB-A ports.

Designed for speedy transfers, this portable 4TB SSD features sequential read speeds up to 800 MB/sec and utilizes a USB 3.1 Gen 2 Type-C host connection. Drop proof up to 6.5', the Crucial X6 also resists random vibrations up to 3.1G during operation and up to 1500G when not in use. Furthermore, this drive can weather extreme temperatures, and features a lightweight and portable design for easy transport. Compatible with laptops, consoles, tablets, phones, and more, the Crucial X6 works with Windows, Mac, and Android operating systems.

  • 4TB Total Storage Capacity
  • USB 3.1 Gen 2 Type-C Connector
  • Up to 800 MB/s Sequential Read Speed
  • Drop, Shock, Vibration & Temp Resistant
  • Lightweight & Portable Design
  • Compatible with Laptops, Consoles & More
  • Works with Windows, Mac, & Android OS

Real-world read performance

The trouble with testing SSDs is that brand-new performance can break down with usage, sometimes quickly. Hence real-world testing is instructive, and only time tells the true tale.

It’s not a good value if performance breaks down in a few days (as it did here), or even within a year. I want my SSDs to be solid for at least 3 years.

Real-world performance tests were performed after the benchmarks, that is, with the device having already been written in full for its full capacity and more.

Carbon Copy Cloner clone

Cloning is a write operation. The Crucial X6 showed severe performance slowdows on a subsequent 1.2TB Carbon Copy Cloner clone operation (as slow as 45MB/sec on large files = pathetic). Surprising, because even a 2nd DiskTester fill-volume did not show issues. But something in the drive must 'fail'—flash usage history or perhaps heat.

The X6 must be considered a low performance budget offering, taking 5.5X longer than the SanDisk ExtremePRO V2.

Clone 355132 files totaling 1276GiB = 1370GB in 120:53 = 180MiB/sec = 188 MB/sec. <=== pathetic

Data verification — icj verify

The Crucial X6 only verifies at about 2/3 of the speed of the Samsung T7 Shield or SanDisk ExtremePRO V2. Clearly, you get what you pay for—grossly inferior performance. I am personally annoyed at devices that test well when new... a way to game the system.

Tested using IntegrityChecker Java on a 1278 GiB set of files, Crucial X6 performance is decent at 642 MiB/sec = 673 MB/sec—but that’s only 2/3 the speed of its (more expensive) competitors.

icj verify T7...
100%: 350398 files 1278.0 GiB @ 642 MiB/sec, 33:58

SSD Performance compared, cloning and data verification

Sustained performance

Tested using the fill-volume command of diglloydTools DiskTester. diglloydTools disktester and its fill-volume command characterizes any SSD or hard drive.

Very strong performance—highly consistent and near the limits of the USB-C bus. It is slightly slower than the SanDisk Extreme PRO V2, but at less than half the price, the value proposition is unbeatable. The difference is unlikely to matter for most use-cases and anyway, a device like the OWC Envoy Pro FX is far faster than either if speed matters a lot.

The sustained write speed is particularly impressive, since some SSDs can crumble under sustained writing. Crucial is using all-fast flash, not a mixture of fast/slow flash memory.

Write speed: 920 MiB/sec = 965 MB/sec
 Read speed: 895 MiB/sec = 895 MB/sec

Transfer size KiB =1024, speed in MiB = 1024 * 1024. Multiply by (1024/1000)^2 for MB/sec.

4TB Crucial X6 Portable SSD: sustained performance across the 2TB capacity

Speed vs transfer size

Tested using the run-sequential-suite command of diglloydTools DiskTester.

Transfer size to IOPS: IOPS = 1024 * MiB/sec / transfer size KiB
eg 258 MiB/sec with 32KiB transfers = 8256 read IOPS/sec, 29760 write IOPS/sec

Outstanding write performance; significantly faster than the 4TB Samsung T7 Shield.

Read speeds are impressively good, easily outperforming both the 4TB Samsung T7 Shield SSD and the SanDisk Extreme PRO V2 on real-world write sizes up to 1 MiB. Peak read speed is a little slower, but speed on smaller writes is much more important. An incredible performance!

Transfer size KiB =1024, speed in MiB = 1024 * 1024. Multiply by (1024/1000)^2 for MB/sec.

4TB Crucial X6 Portable SSD: speed in MB/sec versus transfer size


BH Photo loaned MPG the about $229 4TB Crucial X6 Portable SSD CT4000X6SSD9 for testing. Please buy it at B&H to help support testing here at MPG.

The Crucial X6 4TB Portable SSD is a budget SSD that tests well while new, then quickly goes to crap performance.

While becnhmarks show it beating the SanDisk 4TB Extreme PRO Portable SSD V2 and Samsung T7 Shield SSD on some important metrics, real-world performance showed a plunge in performance shortly after the benchmarks were done. It’s almost as if it were designed to perform well out of the box and then go to crap, hoping that most users would not notice.

Those looking for the very best performance should look at Thunderbolt SSDs, such as the OWC Envoy Pro FX and the OWC Thunderblade which deliver up to 3X the speed.


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