1. A high availability (HA) method for improving utilization of physical servers in a cloud computing resource pool, wherein the method comprises: when the physical servers in the cloud computing resource pool fail, judging whether idle memory of the normally-running physical servers can support running of virtual machines on all the failed physical servers; when the idle memory of the normally-running physical servers can support the running of the virtual machines on all the failed physical servers, restarting the virtual machines on all the failed physical servers on the normally-running physical servers.