System for exclusively controlling access of a semiconductor memory module using a backup memory and compression and decompression techniques

An I/O subsystem including a plurality of channel adapters for serving as interfaces to and from a host apparatus, a plurality of I/O devices, a plurality of device adapters for serving as interfaces to and from the I/O devices and a resources manager for managing the resources of said I/O subsystem as a whole, the subsystem comprising:

• a semiconductor memory module which is composed of a plurality of semiconductor memory chips as one of said I/O devices;
• a spare memory module;
• a data buffer for storing uncompressed data sent from the host apparatus;
• a data compressing means for compressing the data stored in said data buffer;
• a memory interface adapter for controlling the operation of writing the compressed data into said semiconductor memory module and controlling the operation of writing the uncompressed data stored in said data buffer into said spare memory module;
• a verifying means for restoring the compressed data which is written into said semiconductor memory module, and verifying said compressed data by comparing said restored data with the uncompressed data stored in the spare memory module;
• a backup memory for storing the uncompressed data;
• and
• means for writing the uncompressed data into said backup memory when said semiconductor memory module becomes full during the operation of writing the compressed data into said semiconductor memory module because the size of the compressed data is larger than the size of the uncompressed data and subsequently writing the uncompressed data from said backup memory into said semiconductor memory.