Public bug reported:

I have a Lenovo server with a LSI controller that insists on having a
RAID set to boot. So the BIOS is configured with a RAID0 stripe set,
with a single disk:

$ dmraid -i -si
*** Group superset .ddf1_disks
--> Subset
name   : ddf1_4c5349202020202080861d60000000004711471100001450
size   : 974608384
stride : 128
type   : stripe
status : ok
subsets: 0
devs   : 1
spares : 0

Notice that 'devs' is 1.

This causes this bit of code in dm-activate to bail:

        case "$Raid_Type" in
                stripe)
                        if [ "$Raid_Nodevs" -lt 2 ]; then
                                if [ -n "$Degraded" ]; then
                                        log_error "Cannot bring up a RAID0 
array in degraded mode, not all devices present."
                                fi
                                return 2
                        fi
                        ;;

Of course, the above is totally bogus, a 1 disk RAID0 is perfectly
valid. I wonder if this should be testing 'status' instead?

This is a problem because of GPT partitioning. If you don't start the
RAID downstream tools will attempt to partition sda. The RAID metadata
at the end of the disk collides with the GPT partition backup and it
ends up destroying the RAID set and making the server unbootable. The
kernel hints at this condition:

[    4.202136] GPT:Primary header thinks Alt. header is not at the end of the 
disk.
[    4.202137] GPT:974608383 != 976773167
[    4.202138] GPT:Alternate GPT header not at the end of the disk.
[    4.202138] GPT:974608383 != 976773167

Which is 100% true, the GPT was written to the RAID, not the raw disk,
and 974608383 sectors is at the end of the raid volume.

** Affects: dmraid (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1361842

Title:
  dmraid does not start on boot for single disk RAID0

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