Hi everyone,
this week I had a similar problem when I tried to re-install a cdot cluster. In my case it was a 2554 single-node system with SATA disks, which was shipped with ONTAP 9.0.
I booted the system and did "Install new software first" to load ONTAP 9.1. After this I went to maintenance mode to unpartition the disks und remove the ownership. I ran into the following error:
*> disk unpartition 0a.00.12
Disk 0a.00.12 must not have file system partitions. All partitions must be spare
Do not proceed with unpartition if disk has file system partitions. Abort unpartition (y/n)? n
disk unpartition: 0a.00.12 has partitions that are not spare.
Jan 19 10:18:43 [pfhn-cl3-01:raid.unpartition.disk.fail:notice]: Disk unpartition failed on Disk 0a.00.12 Shelf 0 Bay 12 [NETAPP X306_HMRKP02TSSM NA00] S/N [P5JTUG5V], error CR_DISK_WRONG_STATE, additional error info ().
I got 4 disks which could not be unpartitioned and the reinstall did not went through.
Finally I netbooted ONTAP 9.0, went to maintenance mode and were able to unpartition the disks. After this the reinstall was possible.
it seems that in my case ONTAP 9.1 can not deal correctly with partitions created prior ONTAP 9.1 - So it would be interresting if a netboot of ONTAP 9 in your case would also solve the problem.
Then there would be an general issue in ONTAP 9.1 in combination with disk unpartioning.
Kind regards
Marc