Migrate-root time outand error on -resume

[Linuxed]

I have an interesting one. We're migrating our root aggr0 due to shelves being retired.

I followed this KB:  How_to_non-disruptively_migrate_a_nodes_root_volume_aggregate_onto_new_disks_in_ONTAP_9

I'm on 9.1.16p4 so following the 9.2 and above directions. I followed the progress of the aggr being backed up etc. and it was going through restore when it timed out at 600sec.

"Timeout the operation “copy_root_volume_contents_iterator:: create_imp()” took longer than 600 seconds to complete [from mgwd on node {ha partner} (VSID: -3)" 
so after a call to Netapp today an engineer agreed to use the resume command. "::*> system node migrate-root -node node1 -resume true"
That immediately failed "Complete: Internal error. Failed to online the aggregate "n03_aggr0". Reason: Aggregate "n03_aggr0" is already online. [1]

The netapp engineer (yes engineer) and myself are stumped. 

Further documentation (not specific error) said it needs to be repaired in diag mode and to contact netapp.

[TMACMD]

xperience says to open a case fdr this. It could be any number of issues include "too much data" to copy or performance on the node....some odd things. Could be your ONTAP version

Please open a support ticket to dig into this to resolve

[Linuxed]

So it is possible (given the time) the system configuration backup may have caused the failure. In any case we had to go into diag remove the old root and point the dis, and diskroot to the new volume. renamed the root aggr &vol. (much more detail) and eventually failed it back.
My advice is look at the config backup schedules before you start your migration to avoid this headache.