Oracle Exalogic is a multihomed system where multiple IP addresses are configured on the InfiniBand network interface. NFSv4 addresses file locking problems on multihomed systems, such as Exalogic. The file locking problem occurs when NFSv3 is used.
NFSv3 is a stateless protocol. NFS clients do not maintain the state between requests; the clients rely on the Network Lock Manager (NLM) protocol to support file locking. There are known limitations on the NLM based locking, and NFSv3 it can cause lock ownership issues under certain multihomed system configurations, where the source IP addresses are not deterministic between lock and unlock requests.
Unlike NFSv3, NFSv4 is a stateful protocol. An NFS client obtains a client ID assigned during the initial negotiation phase and uses it for all subsequent requests. With the use of Client ID, the client IP address is not used in the file locking process. Therefore, the file locking problem on Exalogic does not occur when NFSv4 is used. In addition, with locking built into the protocol, NFSv4 provides better lock performance than NFSv3.
NFSv4 requires a naming service, such as Network Information Service (NIS) or LDAP, for ID mapping. You can continue to use the naming service on your existing network. The naming service is not related to the file locking problem.
Note:
It is assumed that you have a working NIS or LDAP service on your network. This chapter does not describe how to set up the NIS or LDAP service.