Efficient and Consistent Para-Virtual I/O System

摘要

Embodiments of the invention relate to a para-virtual I/O system. A consistent para-virtual I.O system architecture is provided with a new virtual disk interface and a semantic journaling mechanism. The virtual disk interface is extended with two primitives for flushing and ordering I/O, both of the primitives being exported to para-virtual I/O drivers in a guest operating system. The ordering primitive guarantees ordering of preceeding writes, and the flushing primitive enforces order and durability. The guest drivers selectively uses both of these primitives based on semantics of the data being persisted from the para-virtual cache hierarchy to physical disk. The order of committed writes is enforced in order to enable a consistent start recovered after a crash.

主权项

1. A method comprising:
a virtual machine operating in communication with a host machine, including the virtual machine employing a guest operating system with guest page cache and guest disk cache, and the host machine employing a host operating system with host page cache, the caching layers forming a para-virtual storage system; receiving a flush request in a virtualized file system; classifying the received flush request for selection between a write order command and a write flush command, wherein write order provides asynchronous ordering for processing the flush request, and write flush provides synchronous ordering for processing the flush request; selectively employing the write order and write flush commands based on the classification of the received flush command, and returning a converted request form the classification, the conversion determined by one of the classified selections; processing the converted request, including enforcing an order of committed writes; and a consistent virtual disk image provided through enforcement of the order.