Local Migration of VDM root filesystems

Hi! We are in the process of removing a storage pool (back end storage being retired). I have migrated all the filesystems off of the old storage pool, but I am still seeing three via cli that are not showing up in Unisphere:
[nasadmin@GAQEMCNAS01 ~]$ nas_fs -query:StoragePoolName==symm_ata -format:'%d\n' -fields:Name
root_fs_vdm_vdm01_1
root_avm_fs_group_21
root_fs_vdm_vdm02

Few questions I hope someone can answer:

I figured out that the root_fs_vdm_vdm0* filesystems are the rootfs of the two VDMs we have, but what is the root_avm_fs_group_21?

I assume I will have to get the rootfs of the VDM's off that storage pool before I delete it. Can I just do a local replication of the VDM to the new storage poo, and if so, do I just replicate it and do the failover? That won't effect the filesystems currently mounted to it will it, since it is a local replication and I have already moved the filesystems mounted to those VDMs to the new storage?