As part of the RAID work (T84050 etc.), I added a fact that encodes all the RAID configured on every server, in a comma-separated list.
Auditing that list from servermon's fact query to include hosts where no RAID is configure and `is_virtual` equals to `false`, results in this:
[x] bast4001.wikimedia.org (T133699)
[x] chromium.wikimedia.org & hydrogen.wikimedia.org (T123727)
[x] labnet1002.eqiad.wmnet (T136718)
[x] lvs100.wikimedia.org, being decom'd in favor of new hardware in T184293 (T136737)
[x] maps-test200.codfw.wmnet (T140440) actually had RAID but was not detected
[x] mw* (T106381)
[x] osmium.eqiad.wmnet (T132530)
[x] rcs100.eqiad.wmnet (T140441)
[ ] rdb100.eqiad.wmnet (T140442)
[x] snapshot100.eqiad.wmnet (T140439)
This list is quite troubling; it's also troubling that for many of those hosts, we do have second disks, but they were never configured. That's the case for e.g. `rdb1005`/`rdb1006` or `chromium`:
root@chromium:~# fdisk -l /dev/sdb
Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders, total 976773168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000081
Device Boot Start End Blocks Id System
All of the above should audited and reformatted to be using RAID, when needed.
The list is by no means exhaustive; there are other hosts that are reported as having a RAID controller, but perhaps they are configured as JBOD (or single-disk RAID0s). Hosts with just the "mpt" controller reported are especially susceptible to that (e.g. labnet1001 was not on the list above, but has no RAID configured).