Red Hat Knowledgebase

This problem arises due to open to close cache consistency feature which was added to kernel-2.4.20. This feature was introduced to ensure cache coherency among different NFS clients. When an application on a NFS client opens a file stored on a server, the client checks for the existence of the file and its permissions by sending a GETATTR call. When the file is being closed, any changes are written to the server so that the next client viewing the file can see the changes. The open to close cache consistency feature is implemented by comparing the results of GETATTR just after a file is closed and just before the same file is opened. If the results are the same, the client's cache is valid, else the cache is purged.

The GETATTR calls reduce the performance because of the huge amount of network traffic that it generates. This can be avoided by using the mount option nocto. However, this would only come at a cost of the integrity of the data because it breaks the cache inconsistency if there are several clients accessing the same file. The other option is to use Red Hat Enterprise Linux version 4. Kernel 2.6 uses a different mechanism to ensure data consistency.