I am having the same issue. When I mount a datastore to a location using NFS 4.1, without Kerberos, and the access mode is read-write, the share mounts but as read-only. In vSphere when I check Datastores it shows "Datastore (read only)". My datastore NFS location is Windows Server 2012. Also, NFS 4.1 doesn't work at all on Windows Server 2008 R2. Is 4.1 not supported on 2008 R2?
Here is what the vmkernel.log shows:
2015-11-30T21:24:08.677Z cpu1:34017 opID=8fce142c)NFS41: NFS41_VSIMountSet:402: Mount server: VSVR12-01, port: 2049, path: /VMs, label: Datastore, security: 1 user: , options: <none>
2015-11-30T21:24:08.677Z cpu1:34017 opID=8fce142c)StorageApdHandler: 982: APD Handle Created with lock[StorageApd-0x4306a72bc140]
2015-11-30T21:24:08.680Z cpu1:33354)NFS41: NFS41ProcessClusterProbeResult:3865: Reclaiming state, cluster 0x4306a72bd2c0 [26]
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSCompleteMount:3582: Lease time: 120
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSCompleteMount:3583: Max read xfer size: 0x3fc00
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSCompleteMount:3584: Max write xfer size: 0x3fc00
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSCompleteMount:3585: Max file size: 0xffffffff000
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSCompleteMount:3586: Max file name: 255
2015-11-30T21:24:08.691Z cpu1:34017 opID=8fce142c)WARNING: NFS41: NFS41FSCompleteMount:3591: The max file name size (255) of file system is larger than that of FSS (128)
2015-11-30T21:24:08.692Z cpu1:34017 opID=8fce142c)WARNING: NFS41: NFS41FSCompleteMount:3601: RECLAIM_COMPLETE FS failed: Failure; forcing read-only operation
2015-11-30T21:24:08.693Z cpu1:34017 opID=8fce142c)NFS41: NFS41FSAPDNotify:5651: Restored connection to the server VSVR12-01 mount point Datastore, mounted as 2bf37a9c-ba7ba30d-0000-00000000
2015-11-30T21:24:08.693Z cpu1:34017 opID=8fce142c)NFS41: NFS41_VSIMountSet:414: Datastore mounted successfully
2015-11-30T21:24:15.677Z cpu1:423423)WARNING: LinuxSignal: 181: Signal 20 has unimplemented cartel-level semantics (sending anyway)
- vmkernel.log 4692/4692 100%
Any help would be appreciated!