Providing automated quality-of-service (‘QoS’) for virtual machine migration across a shared data center network

1. A method of providing automated quality-of-service (‘QoS’) for virtual machine migration across a shared data center network, the method comprising:

identifying, by a virtual machine migration module, a virtual machine to migrate from a source host to a destination host;

determining, by the virtual machine migration module, a migration cost for migrating the virtual machine from the source host to the destination host including:

determining an amount of data to be transmitted from the source host to the destination host when migrating the virtual machine from the source host to the destination host; and

determining a maximum amount of time available for migrating the virtual machine from the source host to the destination host;

identifying based on the migration cost, by the virtual machine migration module, a least congested network path between the source host and the destination host and a bandwidth to be used for migration;

receiving a user specified time limit for completing the migration over the identified least congested network path; and

initiating, by the virtual machine migration module, transmission of the virtual machine from the source host to the destination host over the least congested network path,

including reserving bandwidth across the shared data center network for transferring the virtual machine from the source host to the destination host in dependence upon the migration costs,

wherein reserving bandwidth includes setting a transmission rate to a value, and

wherein the amount of data to be transmitted from the source host to the destination host is to be transmitted over the least congested network path at the transmission rate within the maximum amount of time available for migrating the virtual machine from the source host to the destination host.

2. The method of claim 1 wherein the amount of data to be transmitted from the source host to the destination host is determined in dependence upon a memory size of the virtual machine, network bandwidth to be used for migration, a maximum allowed downtime for the virtual machine, and a dirty page rate for the virtual machine.

3. The method of claim 1 further comprising:

wherein the shared data center network comprises switches and the least congested network path comprises switches,

creating, by the virtual machine migration module, two messaging queues on each of the switches in the shared data center network, including a migration queue for virtual machine migration network traffic and a general queue for general network traffic and setting bandwidth associated with the migration queue on each of the switches on the least congested network path to a value predicted by a migration cost model.

4. The method of claim 3 wherein initiating transmission of the virtual machine from the source host to the destination host over the least congested network path, includes:

specifying port numbers used for migration;

identifying migration traffic based on the specified port numbers used for migration; installing specific rules on all switches on the least congested network path to enqueue all traffic between source and destination hosts with the port numbers to the migration queue; and

initiating transmission of the virtual machine from the source host to the destination host using the migration queue of each of the switches in the least congested network path between the source host to the destination host.