Synchronous management of disk flush requests

摘要

In a process for migrating a virtual machine's storage from a source disk to a destination disk, a virtual machine monitor (VMM) records a source-generation count representing contents on the source disk, a writes-mirrored value representing a number of writes replicated from the source disk to the destination disk at a time contents of the disks were equal, a flush-request value representing the source-generation count at a time a flush is requested by a guest operating system of the virtual machine, and a writes-flushed value representing the writes-mirrored value at a time of a last flush of the destination disk. Upon identification of a steady state, the VMM sets the writes-mirrored value to the recorded source-generation count. The VMM determines if a request to flush the source disk has been issued by the guest, sets the flush-request value to the source-generation count at a time of the flush request, and flushes the destination disk upon determining that the flush-request value is greater than the writes-flushed value and the flush-request value is less than or equal to the writes-mirrored value.

主权项

1. A method comprising:
recording, by a virtual machine monitor executed by a processing device, a source-generation count representing content on a source disk associated with a virtual machine; recording a writes-mirrored value representing content on a destination disk migrated from a source disk, at a time contents of the source disk and the destination disk were equal; recording a flush-request value representing the source-generation count at a time a flush is requested by a guest operating system of the virtual machine; recording a writes-flushed value representing the writes-mirrored value at a time of a last flush of the destination disk; identifying, by the virtual machine monitor, a steady state wherein contents associated with a virtual machine stored on the source disk and a destination disk are equal; upon identifying the steady state, setting a writes-mirrored value to the recorded source-generation count; determining if a flush request to flush the source disk has been issued by the guest operating system of the virtual machine; setting the flush-request value to the source-generation count at a time of the flush request; and flushing the destination disk upon determining that the flush-request value is greater than the writes-flushed value and the flush-request value is less than or equal to the writes-mirrored value.