Limitations of the NFS File Lock Migration Feature

Multiple NFS packages are not supported on the same node

The file lock migration feature will not work for multiple NFS packages running on the same node. So, if file lock migration feature is enabled then any node configured for NFS package in a cluster, cannot be configured to run multiple NFS packages. This limitation is because statd/sm-notify on Linux does not deal with multi-homed hosts. It does not support multiple IP addresses in sending server reboot notification.

Multiple Package IPs are not supported with NFS

A Serviceguard package can support multiple relocatable IP addresses associated with it. But, if lock migration feature is enabled then only one IP should be specified for NFS in the package control script as the NFS server reboot/failover notification can be sent using only one relocatable IP.

NFS Defect

The NFS File Lock Migration feature is only supported in SLES 9 SP 1 (and later), and Red Hat 4 Update 4 (and later). This is due to a defect in NFS, the file lock migration feature does not work on base SLES9, RH4 U1, RH4 U2 and RH4 U3.

Do not use NFS Server as an NFS Client

During package halt, SIGKILL signal is sent to the lockd kernel thread to release file locks so that the filesystem can be unmounted successfully. If the server is also an NFS client, it loses the NFS file locks obtained by client-side processes when SIGKILL signal is sent to the lockd kernel thread with an intention to release server side locks. So, if the client applications use NFS file locking, it is suggested not to use the clustered nodes configured for the NFS package as an NFS client for any server.

SERVICE_FAIL_FAST_ENABLED should be set to “YES”

SERVICE_FAIL_FAST_ENABLED should be set to “YES” for the NFS monitoring service in order to have lock migration feature work consistently. (See the “Configuring Lock Migration Feature” section in Chapter 2 for more details)