I was just today doing at restore of a vCenter 7.0 from a VCSA backup, and in stage 2, when it validated the backup file and checks the newly deployed VCSA, it returned the following error/failure.
Metadata and system validation failed. Error: Unknown system resource type seat Error: Unknown system resource type vtsdb
This error come because the old vCenter server had 2 disks extended (seat and vtsdb), so I had to check in the backup meta data file “backup-metadata.json” for the original size of this disk, and exspanded the VMDK files, and the volume.
Afterwards the restore continued.
NOTE: Another solution could be to edit the size in the “backup-metadata.json” (make a backup before editing), but make sure you do not make the disks/mounts to small to contain the data. I don’t know if this is support, so do this at you own risk.