Patent ID: 8738671

Claim:
A method for managing global cache coherency and access permissions in a distributed shared caching for clustered file systems (CFS) in a clustered file system in a computing environment, the method comprising: providing the CFS for residing on a cluster of nodes for accessing space of data segments that are shared between the cluster of nodes; providing, in the CFS, a local cache memory of data segment slots on each of the cluster of nodes and a distributed shared memory (DSM) module, with no internal memory for the data segments on each of the cluster of nodes, wherein the local cache memory acts as an external memory; managing the access permissions to an entire space of the data segments by using the DSM module; and while processing a request message from a remote DSM module to access one of the data segments: including in a response message a permission to access the one of the data segments, and deciding if one of a transfer of ownership and most recent contents of the one of the data segments should be included in the response message for the permission to access the one of the data segments, wherein last two components of the response message depend upon availability of the one of the data segments that is requested in a local external cache.