[oVirt shell (connected)]# create disk --vm-identifier MyVM --provisioned-size 8589934592 --interface virtio --format cow should read --provisioned_size, not --provisioned-size.
Found at https://access.redhat.com/knowledge/docs/en-US/Red_Hat_Enterprise_Virtualization/3.1-Beta/html-single/CLI_Guide/index.html
Changed to --provisioned_size