Disk controller with volatile and non-volatile cache memories

A disk storage subsystem comprising:

• at least one disk drive;
• and
• a disk controller coupled to said disk drive and adapted to couple to a host computer, said disk controller comprising:
• a controller microprocessor;
• a cache memory including:
• a plurality of volatile memory modules which form a read-cache;
• a plurality of non-volatile memory modules which form a write-cache;
• and
• a cache memory control circuit coupled to said non-volatile memory module and said volatile memory module wherein in response a write command received from the host computer, said controller microprocessor allocates a predetermined number of memory blocks in each of said volatile and said non-volatile memory modules for storage of write data and upon completion of a write operation to said non-volatile memory modules, said cache memory control circuit transfers the write data from said non-volatile memory module to said volatile memory module.

A method of transferring data to be written from a host computer to at least one disk drive within a disk storage subsystem including a host interface circuit, a disk interface circuit, a controller microprocessor, a cache memory, a cache memory management circuit and the at least one disk drive, the method comprising the steps of:

• receiving in the disk storage subsystem a host write-to-disk command;
• allocating a predetermined number of memory blocks in a non-volatile memory module of the cache memory;
• allocating a predetermined number of memory blocks in a volatile memory module of the cache memory;
• storing the data to be written to the at least one disk drive in the allocated memory blocks of the non-volatile memory module of the cache memory;
• and
• initiating a DMA transfer by the cache memory management circuit, to copy the data to be written to the at least one disk drive from the allocated memory blocks of the non-volatile memory module to the allocated memory blocks of the volatile memory module of the cache memory.

A method of controlling a cache memory of a disk storage subsystem coupled to a host computer, the method comprising the steps of:

• establishing a list of available memory blocks in a write-cache;
• in response to a write operation initiated by a host computer, allocating from the list of available memory blocks a predetermined number of memory blocks of the write-cache;
• allocating a like predetermined number of blocks in a read-cache;
• receiving write-data from the host computer;
• storing the write-data in the allocated memory blocks of the write-cache;
• indicating to the host computer that the write-data stored in the read-cache is valid and available for use;
• and transferring the write-data from the allocated memory blocks of the write-cache to the allocated memory blocks of the read-cache.