Incorrect backing device type

Issue

When adding a LUN to the guest, the following error occurs:

# hpvmmodify -P guest1 -a disk:avio_stor::disk:/dev/rdisk/disk(xx)

hpvmmodify ERROR (guest1): Incorrect backing device type.
hpvmmodify Unable to create device disk:avio_stor::disk:/dev/rdisk/disk(xx)
hpvmmodify Unable to modify the guest.

Solution

Ultimately, the problem causing the failure stems from a mismatch of minor numbers between the /dev/(r)disk/disk(xx) and the /dev/pt/pt_disk(xx) used by HP VM. Looking at it a bit closer you will see the following:

# ll /dev/disk/disk(xx)

brw-r-----   1 bin        sys          1 0x00002e Dec 22 11:40 /dev/disk/disk(xx)

# ll /dev/rdisk/disk(xx)

crw-r-----   1 bin        sys         13 0x00002e Dec 22 16:04 /dev/rdisk/disk(xx)

# ll /dev/pt/pt_disk(xx)

crw-r-----   1 bin        sys         12 0x000026 Dec  2 11:56 /dev/pt/pt_disk(xx)

Typically, if you look at what disk is using the minor number associated with the /dev/pt device you will agree that it is not a valid backing device type. For example, an EFI partition:

# ll /dev/disk | grep 0x000026

brw-r-----   1 bin        sys          1 0x000026 Dec 10 11:24 disk(yy)_p1

The solution is to remove the offending pt_disk(xx), remove the hpvm_devinit file and then rescan/create VM devices using hpvmdevmgmt –I

# rm /dev/pt/pt_disk(xx)

# rm /var/opt/hpvm/common/hpvm_devinit   

# hpvmdevmgmt –I

Per the hpvmdevmgmt man page:

NOTE: The hpvmdevmgmt -I command works only on device directories that have changed. If you want the command to rigorously search all device directories regardless of whether changes have happened since the last search, remove the /var/opt/hpvm/common/hpvm_devinit file before running hpvmdevmgmt –I

Finally, looking at /dev/pt/pt_disk(xx) we can see that it now matches the minor number for the files in /dev/disk and /dev/rdisk for disk(xx):

# ll /dev/pt/pt_disk(xx)

crw-r-----   1 bin        sys         12 0x00002e Dec 27 16:40 /dev/pt/pt_disk(xx)

Once that change is complete, the disk should add as expected.