Expert Evaluation
merit
- Very fast in RAID 0
- Includes various RAID software
- Easy SSD installation.
- Come back cool
disadvantage
- Disappointing performance of individual drives
- No hardware RAID
Our Verdict
Fully populated with RAID 0, the OWC Express 4M2 is a 4-slot NVMe/M.2 enclosure that offers plenty of capacity and very good performance. Other configurations will be slower, especially in non-RAID mode.
Price upon review
$250 without SSD and RAID software, $380 without SoftRAID software and SSD
Lowest Price Today: OWC Express 4M2 Thunderbolt NVMe Enclosure
$249.99
$249.99
The OWC Express 4M2 is a fast Thunderbolt 3 enclosure that lets you build massive, performance-oriented external storage utilizing up to four NVMe SSDs. These can be used as individual drives/volumes or combined into RAID. (You must provide your own NVMe SSD modules.)
It’s pretty versatile, but RAID is the reason to buy the Express 4M2. However, the non-RAID single SSD performance was disappointing.
OWC Express 4M2: Features and Specifications
The Express 4M2 is a Thunderbolt 3 enclosure with two Thunderbolt 3 ports and a full-size DisplayPort port. This reveals a bit of the device’s previous design. Inside, there are four M.2 slots that support PCIe 3.0. This reveals another.
The OWC website doesn’t list any limits on how much SSD you can install, so it looks like you can probably fit up to 32TB at the moment.
The enclosure is just under 2.5 inches tall (including the rubber feet), just over 4.5 inches deep, and nearly 5.4 inches wide. There’s a fairly large fan that needs to be removed to install an SSD (our test unit came empty), but it’s easy to handle, and the fan is very quiet.
As you might have guessed, powering four SSDs requires an AC adapter. In this case, it’s a heavy 6-amp 12-volt unit with a coaxial connector on one end of the drive and a detachable 3-prong cable on the other.
OWC might have been better off renaming the Express 4M2 after releasing its much faster, more versatile (and more expensive) Express 1M2 cousin. It’s a bit of a confusing marketing message, since Express 1M2 is USB 4.
To operate Express 4M2 in RAID, software is required. OWC provides a license for the convenient cross-platform SoftRAID, but the Pro portion that allows volume creation expires 3 years from the date of purchase. SoftRAID operates indefinitely, including rebuilding in case of drive failure.
You could leverage macOS or Windows RAID to the same effect, but then you lose cross-platform usability. Platform independence is one of the reasons I still prefer hardware RAID.
OWC Express 4M2: Speed ​​and Performance
As I’ve already said, the Express 4M2’s performance will vary depending on your drive configuration, but overall it should offer very fast read and write speeds. This will vary depending on what you’re comparing it to.
It’s not as fast as the Express 1M2, which proved to be faster on every bus we tried (from 5Gbps USB to 40Gbps USB 4/Thunderbolt). I’m including the 1M2 results just to show you how much you’re missing.
We tested on the Mac Studio using Disk Speed ​​Test and AmorphousDiskMark, but also tested using our sister publication PCWorld’s test bed and suite. On both platforms, we tested the devices with four single 2TB SSDs (we tested one), a single 8TB volume in striped RAID 0, and a single 4TB volume in RAID 1+0.
Four 2TB PCIe 4.0 NVMe SSDs are adopted, each capable of 5GBps read and 4GB write. The results surprised us a little.
What really surprised us was the single drive performance. This is a PCIe 4.0 NVMe SSD that can easily outrun 40Gbps Thunderbolt 3. We can’t say for sure, but the bandwidth is spread evenly across the four slots, so you’ll probably only get 10Gbps. The results read like this:
Here are the PCWorld test results, which are generally consistent with the macOS test results: fast in RAID 0, slow but fast writes in RAID 1+0, and below-average performance in non-RAID mode.
To get the best performance on Windows (tested against the charts), I had to specifically set up Express. Setting the 4M2 property/policy (SoftRAID software warns you about this) will either cut the best performance or the write speed in half for both RAID modes.
CrystalDiskMark 8 read performance was excellent in RAID 0, and fantastic in RAID 1+0. RAID write performance was good, but not as great as we saw with the 1M2 and Sandisk Pro-G40.
Again, the very weak performance with just a single SSD indicates partial bandwidth allocation. It is certainly faster than a hard drive, but if you want to add four separate volumes, a single drive enclosure is much better. Unless, of course, it has a port. Very few single SSD enclosures offer passthrough.
CrystalDiskMark 8 rated random performance as ‘Good’, the only area where the Express 4M2 catches up outside of RAID mode.
The actual 48GB transfer mimics CrystalDiskMark 8’s conclusions: RAID 0 is best, RAID 1+0 is next, and single SSD mode is worst.
I’m not sure why RAID 1+0 is so slow in writing. It still has to do shotgun writes to both volumes. But keep in mind that this is software RAID, which is dependent on your computer’s CPU. RAID 0 450GB write times are fine for an external drive. RAID 1+0 and single drive times are not.
Overall, the Express 4M2 delivered the desired read and write speeds in RAID 0, and read speeds in RAID 0+1, but was somewhat weaker in single drive mode. The 4M2 also ran very cool in our tests, with plenty of internal airflow and a fan watching it.
Warning: RAID 0 does not provide fault tolerance. While it is reliable, as proven by the latest NVMe SSDs, if one fails, you will lose all your data. I don’t know how much it would cost to recover an SSD RAID setup, but even if it were possible, it wouldn’t be cheap.
Should I buy the OWC Express 4M2?
If you are going to fully populate your Express 4M2 with RAID 0, do so. Performance will generally live up to expectations. Other modes will not. Again, you may be better off using multiple single drives, such as OWC’s excellent, fast, and very versatile Express 1M2.
