GPFS: Administration and Programming Reference - IRA Home

You may also choose to restrict the use of the NFS server node through the normal GPFS path and not
use it as either a file system manager node or an NSD server.
Synchronous writing using NFS
With Linux,write operations are usually asynchronous. If synchronous writes are required over NFS, edit
the /etc/exports file to include sync,no_wdelay.
Unmounting a file system after NFS export
Because NFS use of a GPFS file system may result in a file being held, attempting to unmount a GPFS
file system may return a 'Device is busy' error. If this occurs, stop the NFS daemons before attempting to
unmount the file system at the NFS server. On Linux, issue this command:
/etc/rc.d/init.d/nfs stop
On AIX, issue this command:
stopsrc -g nfs
NFS can be restarted after the unmount completes. On Linux, issue this command:
/etc/rc.d/init.d/nfs start
On AIX, issue this command:
startsrc -g nfs
NIS automount considerations
The default file system type when using the automounter daemon is NFS. When the -fstype option is not
specified, and the server is the local node, a soft-mount of the local directory is done at the desired mount
point. JFS is assumed as the only handler of local directories. A GPFS file system local soft-mount does
not work implicitly, since the mount request is passed to JFS which then produces an error. When
specifying -fstype mmfs the local soft-mount works because the mount is then passed to GPFS instead of
JFS.
A GPFS soft-mount does not automatically unmount. Setting -fstype nfs3 causes the local server mounts
to always go through NFS. This allows you to have the same auto.map file on all nodes whether the
server is local or not, and the automatic unmount will occur. If you want local soft-mounts of GPFS file
systems while other nodes perform NFS mounts, you should have different auto.map files on the different
classes of nodes. This should improve performance on the GPFS nodes as they will not have to go
through NFS.
Chapter 6. Managing GPFS access control lists and NFS export 55