Minimizing downtime when importing virtual machines from other platforms

A system comprising:

• a memory to store a virtual disk image of a source virtual machine (VM) that is to be imported from a source platform to a target platform;
• and
• a processing device operatively coupled to the memory, the processing device to:
• obtain configuration information for the source VM;
• cease operation of the source VM;
• create an overlay image of the virtual disk image of the source VM on an external disk located on a storage domain that is separate from the source platform;
• create a temporary disk on the target platform;
• create a second overlay image of the virtual disk image on the temporary disk of the target platform, the temporary disk comprising an active layer of the external disk, and the external disk comprising a backing file of the temporary disk;
• start a target VM on the target platform in view of the configuration information, wherein the target VM performs read and write operations using the temporary disk;
• and
• copy contents of the temporary disk and the external disk to a target disk on the target platform, wherein the contents of the temporary disk correspond to the read and write operations performed by the target VM.

A non-transitory computer-readable storage medium including instructions that, when executed by a processing device of a source host system, cause the processing device to:

• convert a format of a VM associated with a hypervisor of a source platform to a second format associated with a hypervisor of a target platform, the VM to be imported from the source platform to the target platform;
• create an overlay image of a virtual disk image of the VM on an external disk located on a storage domain that is separate from the source platform, the overlay image recording changes made by the VM during the converting;
• obtain configuration information for the VM;
• create a temporary disk on the target platform;
• create a second overlay image of the virtual disk image on the temporary disk of the target platform, the temporary disk comprising an active layer of the external disk, and the external disk comprising a backing file of the temporary disk;
• start a second VM on the target platform in view of the configuration information;
• and
• copy, by the processing device, contents of the temporary disk and the external disk to a target disk on the target platform, wherein the contents of the temporary disk correspond to operations performed by the second VM.