Well that was a bit scary. My initrd failed to assemble my RAID array after a power outage. I had updated my kernel from 5.0.1 to 5.4.7 and apparently 5.4 now needs "raid0.default_layout=2" in the boot options. There is data corruption if you get the layout wrong, but apparently only if you have mismatched drive sizes (which I don't).
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