Thanks Roger, I appreciate your help and quick reply!
Two of the disks (sda, sdb) were able to return
# smartctl --all /dev/sdX
just fine, but sdc and sdd returned very little, so I dug a bit deeper with
# smartctl -d ata -T permissive --all /dev/sdX
The results are in the pastebin: https://pastebin.com/yWJTPvBa
It looks like only sdd has an error count. I would love to get this up
long enough to recover at least a portion of the data, which isn't
backed up elsewhere.
