NFS v3 versus v4

Solution 1:

NFS 4.1 (minor 1) is designed to be a faster and more efficient protocol and is recommended over previous versions, especially 4.0.

This includes client-side caching, and although not relevant in this scenario, parallel-NFS (pNFS). The major change is that is that the protocol is now stateful.

http://www.netapp.com/us/communities/tech-ontap/nfsv4-0408.html

I think it is the recommended protocol when using NetApps, judging by their performance documentation. The technology is similar to Windows Vista+ opportunistic locking.

NFSv4 differs from previous versions of NFS by allowing a server to delegate specific actions on a file to a client to enable more aggressive client caching of data and to allow caching of the locking state. A server cedes control of file updates and the locking state to a client via a delegation. This reduces latency by allowing the client to perform various operations and cache data locally. Two types of delegations currently exist: read and write. The server has the ability to call back a delegation from a client should there be contention for a file. Once a client holds a delegation, it can perform operations on files whose data has been cached locally to avoid network latency and optimize I/O. The more aggressive caching that results from delegations can be a big help in environments with the following characteristics:

• Frequent opens and closes
• Frequent GETATTRs
• File locking
• Read-only sharing
• High latency
• Fast clients
• Heavily loaded server with many clients