Gluster client node sees lots of "Stale NFS file handle" messages even if NFS is not used, why ?

Issue

• Gluster client nodes sees lots of "Stale NFS file handle" messages even if NFS is not used, why ?

[2013-04-25 10:57:56.888130] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-2: remote operation failed: Stale NFS file handle. Path: (dc7043d4-2105-49f6-b7b0-ce28fe290386)
[2013-04-25 10:57:56.888205] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-3: remote operation failed: Stale NFS file handle. Path: (dc7043d4-2105-49f6-b7b0-ce28fe290386)
[2013-04-25 11:04:21.821738] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-2: remote operation failed: Stale NFS file handle. Path: (b1093b2d-3808-41e0-8388-4eeef75067b8)
[2013-04-25 11:04:21.821816] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-3: remote operation failed: Stale NFS file handle. Path: (b1093b2d-3808-41e0-8388-4eeef75067b8)
[2013-04-25 18:18:57.719487] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-0: remote operation failed: Stale NFS file handle. Path: (c75f16ee-3437-4874-895a-961a74710b94)
[2013-04-25 18:18:57.719567] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-1: remote operation failed: Stale NFS file handle. Path: (c75f16ee-3437-4874-895a-961a74710b94)
[2013-04-25 18:18:57.721086] W [client3_1-fops.c:2630:client3_1_lookup_cbk] 0-tid-client-2: remote operation failed: Stale NFS file handle. Path: (222a0e1d-492a-4233-8718-204c2a262b2d)