Methods to perform disk writes in a distributed shared disk system needing consistency across failures

A method for managing a data item, the method comprising the steps of:

• when a node that has an exclusive lock on a data item desires to write the data item to persistent storage, performing the steps of
• determining whether a mode associated with the data item is local or global;
• if the mode associated with the data item is local, then the node writing the data item to persistent storage without communicating with a master of said data item;
• and
• if the mode associated with the data item is global, then the node sending a message to the master of the data item to request writing of said data item to persistent storage.

A method for managing a data item, the method comprising the steps of:

• when a data item is transferred from one node to another node, performing the steps of
• if the data item has been dirtied by the node and a mode associated with the data item is local, then changing the mode from local to global prior to sending the data item to another node;
• if the data item has not been dirtied by the node and the mode associated with the data item is local, then sending the data item to the other node without changing the mode;
• allowing the other node to write the data item to persistent storage without requesting permission if the mode is local;
• and
• requiring the other node to obtain permission to write the data item to persistent storage if the mode is global.

A computer-readable medium carrying instructions for managing caches in a system with multiple caches that may contain different copies of a data item, the instructions comprising instructions for performing the steps of:

• modifying the data item in a first cache to create a modified data item;
• when a node associated with the first node desires to write said modified data item to persistent storage, performing the steps of:
• if then node associated with the first cache does not currently have ownership rights to said data item, then the node associated with the first cache sending a request to a master of said data item for said data item to be written to persistent storage;
• and
• if said node associated with said first cache currently has ownership rights to said data item, then the first node writing said data item to persistent storage without sending a request to said master for said data item to be written to persistent storage.

A computer-readable medium carrying instructions for managing a data item, the instructions comprising instructions for performing the steps of:

• when a node that has an exclusive lock on a data item desires to write the data item to persistent storage, performing the steps of
• determining whether a mode associated with the data item is local or global;
• if the mode associated with the data item is local, then the node writing the data item to persistent storage without communicating with a master of said data item;
• and
• if the mode associated with the data item is global, then the node sending a message to the master of the data item to request writing of said data item to persistent storage.

A computer-readable medium carrying instructions for managing a data item, the instructions comprising instructions for performing the steps of:

• when a data item is transferred from one node to another node, performing the steps of
• if the data item has been dirtied by the node and a mode associated with the data item is local, then changing the mode from local to global prior to sending the data item to another node;
• if the data item has not been dirtied by the node and the mode associated with the data item is local, then sending the data item to the other node without changing the mode;
• allowing the other node to write the data item to persistent storage without requesting permission if the mode is local;
• and
• requiring the other node to obtain permission to write the data item to persistent storage if the mode is global.