Method and device implementing software virtual disk in computer RAM that uses a cache of IRPs to increase system performance

摘要

Virtual disks are created in RAM having the characteristics of either a write through unit, a write deferred unit, or a repeat save interval unit, which identifies the mode of operation the virtual disk uses in the backup of its RAM data to a backing disk drive. A unit identified as a write through unit proceeds by writing the write I/O data to the virtual disk in RAM and immediately to the backing disk drive. A write through unit does not signal completion of a write I/O data until the data has been written to both the virtual disk in RAM and the backing disk drive. A unit identified as a write deferred unit proceeds by writing the write I/O data to the virtual disk in RAM and immediately from the RAM to the backing disk drive. A write deferred unit will signal completion of a write I/O data to the virtual disk in RAM only and does not wait for the backing disk write to complete. Write deferred units use an IRP held in a cache to clone the I/O data packet with the data source directed from the virtual disk data in RAM, sending this cloned I/O data packet IRP to the backing disk drive. A repeat save interval unit proceeds without backing up the write I/O data immediately to the backing disk and will only write the I/O data to the virtual disk in RAM. A repeat save interval unit employs a timer and when this timer expires on an adjustable interval, a complete save of the contents of the virtual disk in RAM is made to the backing disk drive.