OWC Express 4M2 (0 TB) Four-Slot M.2 NVMe SSD Enclosure with SoftRAID XT, Up to 2800MB/s, Four M.2 NVMe SSD bays, Add up to 32TB of storage

This is a bit of an unusual storage solution - not many comparisons. But its really flexible, easy to use and really neat in size. The fan is brilliant - n throttling on NVME SSDs so the speed of the drives is maintained. Best speeds achieved with all four slots filled. Also, you can use this enclosure to clone NVMEs. Glas I went off the beaten track a bit and down this road.

It works perfectly on my 2018 Mac Mini running Big Sur - very simple plug & play as I'm not using the bundled SoftRAID XT software. I'm only using one of the 4 NVMe slots with a single 2TB drive, so not the fastest configuration but fast enough for my requirements with plenty of room for expansion.

I've tried a few 4x bay NVMe and this is the best for speed, however, for my near silent M1 Max Macbook Pro set-up it is a bit noisy, as others have also mentioned.Easy to install, well built, not as compact as others in the market, but that's an advantage for the airflow and hack/fix (See below). The free industry standard SoftRaid was easy to install and use and I like the reassuring monitoring of the drive's health.I'm running 4x 8tb NVMe SSD in RAID 4, giving me a total of 24TB with a Parity/Redundancy drive. The bottle neck of the Thunderbolt 3 connection, doesn't allow me to give the full potential of drives, but 1327 Write and 1955 Read is more than enough for my 4k-8k editing needs.Important: NVMe SSD Raid are very sensitive to a power-cut, I would definitely not use Raid 0 for size, unless you have a constant back-up - I learnt the hard way. So I would highly recommend getting a UPS for the drive or your whole set-up, this has saved my work on a couple of occasions and "time is money" as they say!The Hack/FixTo get a quieter drive, you can slow down the fan, as it's non-adjustable via software and runs at Max speed. Replace the cable with the:-Noctua NA-SRC10, 3 Pin Low-Noise Adaptor CablesAlso replace the fan with the:-Gelid Solutions Silent 6 – 3-Pin fan of 60mm for Standard Case | Silent Operation | Optimized Fan Blades | High Airflow & High Static Pressure.Highly recommended, a reputable brand, the software is always being updated for the latest OS and customer service is excellent!!!!!

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There are three main problems, two of which are seen in other reviews.The NVMe standard does not really contemplate external PCI enclosures, and macOS (as of 10.14.4) does not consider NVMe PCI SSDs as "ejectable", even in the 4M2. The expectation is that the SSD is directly on the machine's motherboard, in the enclosure, and the machine would need powering-down to install/remove/change an NVMe SSD. Consequently it is ABSOLUTELY VITAL that the NVMe SSDs are stable in operation. Unfortunately the 4M2 is not, at least not when all four slots are occupied and the device is attached via an Apple Thunderbolt<>Thunderbolt 3 (USB C-type) adaptor, unless there is absolutely nothing else on the Thunderbolt bus. No daisy chaining unless everything is Thunderbolt 3.You can fairly trivially observe instability by generating moderate read/write load on all four slots when the 4M2 is part of a daisy chain connecting to a mid-2017 Macbook Air using an OWC Thunderbay 6 enclosure and the 4M2; connecting both to a late 2012 Mac Mini reveals the instability even faster!The logged messages when the unstability kicks in and knocks an NVMe drive offline ("script" because unaccountably log stream uses block-buffered rather than line-buffered output!)$ script -q /dev/null log stream --predicate 'sender == "IONVMeFamily"' --style compact --info --debug...2019-05-08 09:40:23.379 Df kernel[0:4f81] (IONVMeFamily) AppleNVMe Assert failed: 0 == (status)2019-05-08 09:40:23.379 Df kernel[0:4f81] (IONVMeFamily) ProcessingError2019-05-08 09:40:23.379 Df kernel[0:4f81] (IONVMeFamily) file: /BuildRoot/Library/Caches/com.apple.xbs/Sources/IONVMeFamily/IONVMeFamily-387.250.10/IONVMeBlockStorageDevice.cpp2019-05-08 09:40:23.379 Df kernel[0:4f81] (IONVMeFamily) line: 545And that's it. You will have to reboot (and probably power cycle) your Mac in order to see the drive again. Expect a kernel panic on shutdown.Note: this instability does not affect the NVMe slot in the OWC Thunderbay 6.Secondly, there is no support for devices which offer 512-byte blocks. This includes the Samsung 970 EVO (not Plus series). These devices simply will not work in the OWC M42. This is discussed in other reviews here, but OWC's website as of today only says (in a footnote at the bottom of the Technical Specs tab): "This device does not support Samsung 970 EVO Plus series SSDs". You must use 4k-block SSDs.Thirdly, each device gets only only one PCI channel, which will limit the performance of a single 4x NVMe SSD inside the enclosureIt is hard to say that this is an outright *bad* device. It does let one put NVMe SSDs on a Thunderbolt bus, and the NVMe standard itself imposes annoying limitations (not hot-swappability at all). However, not all SSDs (and certainly not the latest and greatest), and not at full 4x speed unless you have four SSDs in the enclosure. It seems stable when occupying a Thunderbolt-3 slot with no daisy-chaining, but it certainly is unreliable in a daisy chain involving a Thunderbolt-to-Thunderbolt3 Apple adaptor. Hopefully a future *firmware* version will address these enclosure-specific flaws, and that the firmware will be extremely easy to install from macOS. If and when that happens, I will gladly update this review.

I loved the idea; of getting a device to connect multiple fast NVME drives to a system over thunderbolt.This is an enclosure; you have to add (up to four) of your own NVME drives to it.Since the drives in the enclosure are replaceable; I use this to add capacity and to reduce wear and tear on my iMacs non-replaceable/unrepairable internal SSD drive.There were initially a number of stability and reliability issues with this enclosure and my iMac; it now seems completely stable and reliable. I am running 11.4 (latest MacOS at time of editing)Note that each SSD installed has 1 lane; and is limited to around 700MBs so you get lower performance than the individual drives are capable of.I used firecuda 510 drives in the enclosure and they work fine.I have only loaded two drives into the system; and then used the Mac built in software raid; (not the software that comes with the drive) to make an array.With that configuration I get around 1200 - 1300 MBs; which is fast enough.I really hate the incredible loudness of the always-on-fan; it would be better if the case was designed to take a larger, slower, quieter fan; the box is otherwise very well made.I am planning to try and move this drive further away from my desk; with a longer cable.