Server for NFS (Windows 2008 R2) crashes as soon as the Clients mounts the NFS share

Recently we got an issue where the NFS server ( Windows 2008 R2 was hosting the NFS share) use to bugcheck as soon as the ESX client was mounting the share.

We found that the size of the NFS share was approximately 189 GB in size. The share was open to everyone and also was the only NFS export on the machine. Also the NFS and RPC drivers were updated as per the KB articles below:

· https://support.microsoft.com/kb/2485543    

· https://support.microsoft.com/kb/2662672   

We analyzed the dumps and found that the issue is due to the fact the NFS share is already mounted on another client. Ideally, when a share is mounted, on the server , we read the monitor file and notify the client holding locks. When the share is mounted for the first time, the monitor file will be empty. But in this case, it is not. We could see that the ._nfs\monitor got corrupted.

After some more probing we found that this system was running W2K3R2 earlier and the same volume was used to export NFS shares then as well. So it seems there is some problem related to memory/buffer allocations in the routine that reads/updates the monitor file.

Renaming the ._nfs on the volume in question resolved the issue and the bugcheck stopped.