Updating and reading data and parity blocks in a shared disk system

A system for updating data, comprising:

• a first storage device storing data at a data block;
• a second storage device storing parity data for the data block, wherein a parity group comprises a data block and corresponding parity data for the data block;
• a first processing unit;
• a second processing unit;
• a storage area;
• program logic executed by the first processing unit, comprising:
• (i) means for receiving update data for the data block;
• (ii) means for obtaining the data at the data block;
• (iii) means for calculating partial parity data from the data at the data block and the update data;
• (iv) means for storing the partial parity data in the storage area;
• (v) means for writing the update data to the data block in the first storage device;
• and
• (vi) means for updating parity data for the parity groups for which partial parity data is maintained in the storage area, wherein each parity group may be stored on at least the first or second storage device.

An article of manufacture for use in programming a first processing unit to update data, the article of manufacture comprising at least one computer readable storage device including at least one computer program embedded therein that causes the first processing unit to perform the steps of:

• receiving update data for a data block, wherein the data block is located in a first storage device, wherein a second storage device stores parity data for the data block, and wherein a parity group comprises a data block and corresponding parity data for the data block;
• obtaining data from the data block in the first storage device;
• calculating partial parity data from the data at the data block and the update data;
• storing the partial parity data in a storage area;
• writing the update data to the data block in the first storage device;
• and
• updating parity data for parity groups for which partial parity data is maintained, wherein each parity group may be stored on at least the first or second storage device.

A method for updating data in a data block utilizing a plurality of processing units, the method comprising:

• receiving update data for a data block at a first processing unit, wherein the data block is located in a first storage device;
• obtaining data from the data block in the first storage device;
• calculating, using the first processing unit, partial parity data using the data from the data block and the update data;
• storing the partial parity data and a corresponding parity group number in a first storage area of the first processing unit;
• storing partial parity data and a corresponding parity group number for other data blocks in a second storage area of at least a second processor unit;
• writing the update data to the data block in the first storage device using the first processing unit;
• updating parity data for parity groups, the parity groups having data blocks and corresponding parity data, each parity data being stored on at least the first or a second storage device;
• and
• transmitting, between the first and second processor units, information stored in the storage areas of the of the first and second processor units upon determining a failure of a storage device occurs.