ONCplus B.11.31.11 Release Notes (5900-1557, February 2011)

3 Known Problems and Workarounds
This section lists known problems, probable causes, and appropriate workarounds.
Problem
There is a possibility for an HP-UX 11i v3 system to experience a system hang under the following
conditions:
• An application writes a huge NFS file to a filesystem using NFS loopback mount.
• Two systems NFS-mount file systems from each other and simultaneously write huge amounts
of data to each other.
Causes
On an HP-UX 11i v3 system with NFS loopback mount enabled, there is a possibility for an
application to consume the entire file cache memory while writing a huge NFS file. This could lead
to a deadlock between the NFS client and NFS server modules.
For example, when the NFS client consumes the entire file cache, the server cannot execute any
of the WRITE requests sent by the client because of the non-availability of file cache memory. This
can result in non-availability of file cache memory for other mounted file systems on the node.
There is a high possibility for this problem to occur if the system is configured with low file cache
memory.
For example, when the filecache_min and filecache_max parameters are configured in the range
of 1% to 5% of the total physical memory.
Workaround
A possible workaround to handle this issue is to disable the use of the file cache by the NFS mount
by using “forcedirectio” NFS mount option.
NOTE: This workaround requires the current NFS file system to be unmounted.
18 Known Problems and Workarounds