Distributed storage system using front-end and back-end locking

A method for performing a read operation on a data block in a shared disk system, comprising:

• (a) receiving a read request with a first processing unit for a data block maintained in a data storage location;
• (b) determining, by the first processing unit, whether the first processing unit controls access to the data block;
• (c) reading the data block after determining that the first processing unit controls access to the data block;
• (d) after determining, by the first processing unit, that the first processing unit does not control access to the data block, obtaining control with the first processing unit to the data block;
• and
• (e) performing the requested read operation on the data block.

A computer system for performing an operation on a data block in a shared disk system, comprising:

• (a) a first processing unit including means for receiving a request with a first processing unit to perform an operation on a data block;
• (b) a second processing unit in data communication with the first processing unit;
• and
• (c) program logic implemented in the first and second processing units, comprising:
• (i) means for determining whether the first processing unit controls access to the data block;
• (ii) means for performing the requested operation with the first processing unit upon determining, by the first processing unit, that the first processing unit controls access to the data block;
• (iii) means for transmitting a first message to a second processing unit that controls access to the data block requesting control of access to the data block upon determining that the second processing unit controls access to the data block;
• (iv) means for transferring control of access to the data block to the first processing unit;
• and
• (v) means for transmitting a second message with the second processing unit to the first processing unit that the first processing unit controls access to the data block.

An article of manufacture for use in programming a first and second processing units in a shared disk system, the article of manufacture comprising computer readable storage media within the first and second processing units, wherein the computer readable storage media has at least one computer program embedded therein that causes the first and second processing units to perform the steps of:

• (a) receiving a request with a first processing unit to perform an operation on a data block maintained in a data storage location;
• (b) determining, by the first processing unit, whether the first processing unit controls access to the data block;
• (c) performing the requested operation on the data block with the first processing unit after determining that the first processing unit controls access to the data block;
• (d) after determining, by the first processing unit, that the first processing unit does not control access to the data block, obtaining control with the first processing unit to the data block;
• and
• (e) performing with the first processing unit the requested operation on the data block.