A cloud service providing system is described. The cloud service providing system includes a first host that runs an active virtual instance, where the active virtual instance is used for providing a cloud service for a user. The cloud service providing system also include a second host that runs a first standby virtual instance. The first host stores, in a first shared memory during running of the active virtual instance, memory data needed for running the active virtual instance, and the second host runs, when the first host fails, the first standby virtual instance based on the memory data obtained from the first shared memory, to cause the first standby virtual instance to provide a cloud service for the user. This application improves timeliness and efficiency of hot standby of memory data, provides a real-time redundancy backup capability, and helps ensure performance of services provided based on backed-up memory data.