The World's Smallest NVMe RAID Array

I love me some redundancy. Software designer Jeff Geerling has designed what he states is the world's tiniest NVMe RAID array. With the introduction of the Raspberry Pi Compute Module 4, the Foundation added support for NVMe SSDs via M.2 (PCIe 2.0). While the standard is nowhere close to PCIe 4.0, it can still aggregate a throughput of 8 GB/s, which is still far faster than the previous PCIe generation. To that end, Geerling decided to take advantage of that M.2 support and designed his RAID array around a trio of Western Digital PC SN520 512 Gb M.2 2230 drives, three M.2 NVMe adapters, a 12-slot M.2 riser card, and the Compute Module 4.

The ALFTELM.2 riser allows users to take the Gen 2 Bus and split it 12 ways, which enables each NVMe drive to take full advantage of the 4-lane upstream interface. With everything in place, Geerling then went on to benchmark his tiny RAID rig, starting with one drive only. After recognizing, formatting, and mounting the drive, Geerling then ran his benchmarking script. He found that just a single WD NVMe drive performed 11X faster than any other storage solutions (including micro-SD) compatible with the Pi.

Utilizing all three WD NVMe drives in a RAID 5 configuration, Geerling found that it's slower than just one drive, with write speeds cut in half. Those slower speeds resulted from the Pi's CPU, which couldn't handle multiple drives' consecutive write speeds. Using a RAID 1 or RAID 10 configuration with paired drives would ultimately boost those speeds but take up more drive space as the data is mirrored rather than written consecutively. That said, Geerling's RAID rig is an excellent platform for those looking to use NVMe drives in pairs without sacrificing desk space.