Today I ran offline diagnostics against the SATA drive that I suspected
of causing DMA errors and two system crashes. These offline diagnostics
confirmed a problem with the drive and eliminated FreeBSD as a source of
the problem. I replaced the drive and I'm watching to see if any of the
mystery errors in FreeBSD return (at this point I don't expect them to,
since it seems to have been a defective drive).
It took a tremendously long time for me to figure out how to fix up the
new drive for use. I'm still not sure what I finally ...