Warm migrations for virtual machines in a cloud computing environment

An apparatus, comprising:

• one or more hardware processors;
• and
• computer memory holding computer program code executed by the one or more hardware processors to migrate a virtual machine on a source host to a target virtual machine on a destination host, the virtual machine having disk and RAM contents, wherein the source host runs an emulator instance having a cutover point, the computer program code configured to execute a sequence of ordered operations:
• mirror contents of the disk onto a target disk associated with the target virtual machine;
• initiate transfer of the contents of the RAM at a transfer rate that is as low as possible as compared to an available transfer rate so as to prevent the emulator instance running on the source host from reaching the cutover point;
• while the contents of the RAM are being transferred at the transfer rate and before the contents of the RAM are depleted, initiate a shutdown of the virtual machine, thereby flushing to disk remaining contents of the RAM;
• mirror the remaining contents of the RAM that have been flushed to disk to the target disk;
• complete the shutdown of the virtual machine, wherein the migration of the virtual machine to the target virtual machine occurs in less than approximately thirty (30) seconds;
• and
• initiate a boot of the target virtual machine from the target disk.

A computer program product comprising a non-transitory computer-readable medium holding computer program code executable by a hardware processor to migrate a virtual machine on a source host to a target virtual machine on a destination host, the virtual machine having disk and RAM contents, wherein the source host runs an emulator instance having a cutover point, the computer program code configured to execute a sequence of ordered operations:

• mirror contents of the disk onto a target disk associated with the target virtual machine;
• initiate transfer of the contents of the RAM at a transfer rate that is as low as possible as compared to an available transfer rate so as to prevent the emulator instance running on the source host from reaching the cutover point;
• while the contents of the RAM are being transferred at the transfer rate and before the contents of the RAM are depleted, initiate a shutdown of the virtual machine, thereby flushing to disk remaining contents of the RAM;
• mirror the remaining contents of the RAM that have been flushed to disk to the target disk;
• complete the shutdown of the virtual machine, wherein the migration of the virtual machine to the target virtual machine occurs in less than thirty (30) seconds;
• and
• initiate a boot of the target virtual machine from the target disk.