You will want to look into hard vs. soft mounts and increase your timeout values.
Check mount options.
NFS partitions can be mounted in one of two ways, hard or soft.
HARD MOUNTS are permanent mounts designed to look just like any
normal, local file system. If a partition that is hard mounted becomes
unavailable, client programs will keep trying to access it forever.
This will cause local processes to lock when a hard mounted disk goes
away. Hard mounts are the default type of mount.
SOFT MOUNTS will fail after a few retries if a remote partition
becomes unavailable. This is a problem if you are writing to the
partition, because you can never be sure that a write will actually
get processed on the other hand, your local processes will not lock
up if that partition does go away. In general, soft mounts should only
be used if you are solely reading from a disk and even then it should
be understood that the mount is an unreliable one. If you soft mount a
partition that will be written to, you are nearly guaranteeing that
you will have problems.