So, given that the bug that caused me to abandon this effort is now fixed, I've restarted this migration, with some important differences:
- I'm reusing my old 2 TB hard drives as temporary storage instead of a USB drive, which seems to be performing better.
- I'm running OpenBSD as a VM inside Linux rather than vice versa, which both allows me to continue to use Linux until OpenBSD is ready, and performs better due to Linux's support for VT-x.
- I'm copying files over an NFS mount instead of hacking an SSH-based solution on top of what is already a fairly clumsy hack.
Hopefully, my data should be fully copied over to OpenBSD by the end of the weekend. I still need to figure out what to do with my backups before I commit to migrating, though.