When you restore a VM from a different hypervisor to create an OpenStack instance, the conversion process includes operations to copy configuration settings and VM data.
The conversion process includes the following stages:
Obtain disk information from the VMware backup, mark disk sizes, and identify any operating system disk (bootable disk).
Identify the operating system and collect configuration information such as CPUs, memory, and NIC information that can be used as context for the restore destination.
Create cinder volumes based on the source volume types, attach the volumes to the VSA proxy, and restore the volumes.
All disks from the VMware backup are converted to cinder volumes.
If the source VM contained up to four virtual machine disks, the VM conversion sets flags on the cinder volume to direct OpenStack to add the volumes to an IDE controller
If the source VM contained more than four virtual machine disks, the VM conversion sets flags on the cinder volume to direct OpenStack to add the volumes to a VirtIO controller.
For volumes added to a VirtIO controller, up to 25 data volumes can be attached to the VSA proxy. This limit includes any volumes already attached to the proxy. For example, if a proxy already has two volumes attached, then only 23 data volumes can be attached.
Create an instance from a volume based on the flavor and other conversion options selected for the conversion.
The flavor determines the number of CPUs and memory, and other conversion settings control the access to the instance, network settings, security groups, and the destination zone, region, tenant , or host.
Launch an instance using the cinder volume marked as OS/bootable.
The rest of the volumes are attached after the instance is running.
Volumes attached to the proxy during the conversion are detached for cleanup.