https://ovirt.github.io/ovirt-engine-api-model/4.5/#services/disks POST /ovirt-engine/api/disks <disk> <storage_domains> <storage_domain id="123"/> </storage_domains> <name>mydisk</name> <provisioned_size>1048576</provisioned_size> <format>cow</format> </disk> First off <storage_domain id="123"/> as a field is ridiculous because there is no JSON equivalent I can determine. Next Why is this a good XML structure? <storage_domains><storage_domain><name>MyStorageDomainName</name></storage_domain></storage_domains> But this is not <storage_domains><storage_domain><id>7aaa2d33-c7ba-46f0-b4fd-4cf48a724e8d</id></storage_domain></storage_domains> Next when trying to create a new disk directly on a VM POST /ovirt-engine/api/vms/396bc7c9-ed4a-4209-b9fd-f93e9a47cd31/diskattachments Name works for XML: <disk_attachment> <bootable>true</bootable> <interface>virtio</interface> <active>true</active> <disk> <description>Boot Disk</description> <format>cow</format> <name>mybootdisk</name> <provisioned_size>1048576</provisioned_size> <storage_domains> <storage_domain> <name>MyStorageDomainName</name> </storage_domain> </storage_domains> </disk> </disk_attachment> But Not for JSON { "bootable": "true", "interface": "virtio", "active": "true", "disk": { "description": "Boot Disk", "format": "cow", "name": "mybootdisk", "provisioned_size": "1048576", "storage_domains": { "storage_domain": { "name": "MyStorageDomainName" } } } } And ID fails for both I think the REST API for creating disks needs some real help. They are deprecating the only one that actually works right /ovirt-engine/api/storagedomains/123/disks Does anyone have the correct syntax in JSON, because the available documentation is almost entirely devoid of any, AND the server response..... wait for it...... "The remote server returned an error: (400) Bad Request." .....that is all