Efficient and Consistent Para-Virtual I/O System

A computer program product for a para-virtual I/O filesystem, the computer program product comprising a computer readable storage device having program code embodied therewith, the program code executable by a processing unit to:

• receive a flush request in the virtualized file system;
• classify 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 employ 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;
• process the converted request, including enforcing an order of committed writes;
• and
• return a consistent virtual disk image provided through enforcement of the order.

A system comprising:

• a para-virtual I/O system architecture, including a virtual machine employing a guest operating system with guest page cache and guest disk cache, and a host machine employing a host operating system with host page cache, the caching layers forming a para-virtual storage system;
• a classifier to classify a received flush request and to classify the received flush request for selection between a write order command and a write flush command, wherein the write order provides an asynchronous order for processing the flush request, and write flush provides a synchronous order for processing the flush request;
• a cache manager to selectively employ the write order and write flush commands based on the classification of the received flush command, and return a converted request form the classification, the conversion determined by one of the classified selections;
• the cache manager to process the converted request, including enforce an order of committed writes;
• and
• a consistent virtual disk image provided through enforcement of the order.