whole cluster freezes if one of the nfs server freezes

[abhig]

Hi,
We are having a cluster with couple of disk servers, compute nodes and a head node. Disk server is nfs mounted on all the compute and head nodes.
The problem is that if any of the disk servers hangs, it freezes rest of the cluster too which is dangerous. Ideally, cluster should not care about the hanged server and run without any problem except files from that server is not visible.
Is there any way I could avoid the problem of freezing cluster because of one hanged server?
Thanks,
Abhi.

[Rubberman]

Here is perhaps the relevant mount option information from the nfs man page:

       soft / hard    Determines the recovery behavior of the NFS client after an NFS request times out.   If  neither
                      option is specified (or if the hard option is specified), NFS requests are retried indefinitely.
                      If the soft option is specified, then the NFS client fails an NFS request after retrans retrans-
                      missions have been sent, causing the NFS client to return an error to the calling application.

                      NB:  A  so-called "soft" timeout can cause silent data corruption in certain cases. As such, use
                      the soft option only when client responsiveness is more important than  data  integrity.   Using
                      NFS  over  TCP  or  increasing the value of the retrans option may mitigate some of the risks of
                      using the soft option.