I think the problem is mostly ENOSPC from fsync() which jettisons data just like EIO on Linux. If you ran out of space, PostgreSQL would only learn about that

I think the problem is mostly ENOSPC from fsync() which jettisons data just like EIO on Linux. If you ran out of space, PostgreSQL would only learn about that while checkpointing, and then retry and carry on. Boom, data loss. Today PostgreSQL would panic on the first ENOSPC from fsync() so the problem is mostly "fixed".