Abstract: The present invention provides a system and/or method for reducing disk space usage and/or improving I/O performance of a computer system through the use of data compression and mapping of data page blocks to reduced size data file blocks. The system and/or method can be used to intercept activity at an interface of a computer system I/O subsystem and then map logical data page blocks to reduced sized physical file data blocks on a one-to-one basis, utilizing a suitable data compression algorithm. The system and/or method also allows data compression to be reversed when reading data from a physical disk storage medium associated with that computer system. The system may be implemented as either a device driver or a module linked to an I/O module of a computer system.