GPFS: Administration and Programming Reference - IRA Home

1. Create and mount the GPFS file system. In the examples, we assume a file system with a local mount
point of /gpfs.
For performance reasons, some NFS implementations cache file information on the client. Some of the
information (for example, file state information such as file size and timestamp) is not kept up-to-date
in this cache. The client may view stale inode data (on ls -l, for example) if exporting a GPFS file
system with NFS.
If this is not acceptable for a given installation, caching can be turned off by mounting the file system
on the client using the appropriate operating system mount option (for example, -o noac on Linux NFS
clients). Turning off NFS caching results in extra file systems operations to GPFS, and negatively affect
its performance.
2. Make sure that the clocks of all nodes in the GPFS cluster are synchronized. If this is not done, NFS
access to the data, as well as other GPFS file system operations, may be disrupted.
NFS relies on metadata timestamps to validate the local operating system cache. If the same directory
is either NFS-exported from more than one node, or is accessed with both the NFS and GPFS mount
point, it is critical that clocks on all nodes that access the file system (GPFS nodes and NFS clients)
are constantly synchronized using appropriate software (for example, NTP). Failure to do so may result
in stale information seen on the NFS clients.
3. Ensure that NFS is properly configured and running.
For Linux nodes, information on configuring NFS can be obtained at www.linuxdoc.org.
For AIX nodes, information on configuring NFS can be obtained at publib.boulder.ibm.com/infocenter/
pseries/index.jsp.
4. Edit the /etc/exports file. Include all of the file systems to be exported. For example, to export the
directory /gpfs/dir1 to the cluster1 node, enter:
/gpfs/dir1 rw,access=cluster1
Export considerations
Keep the following points in mind when exporting a GPFS file system to NFS. The operating system being
used, and version of NFS may require special handling or consideration.
Linux export considerations: For Linux nodes only, issue the exportfs -ra command to initiate a reread
of the /etc/exports file.
Starting with Linux kernel versions 2.6, an fsid value must be specified for each GPFS file system that is
NFS exported. The format of the entry in /etc/exports for the GPFS directory /gpfs/dir1 looks like:
/gpfs/dir1 cluster1(rw,fsid=745)
The administrator must assign fsid values subject to the following conditions:
1. They must be unique for each file system.
2. The values must not change over reboots (the file system should be unexported before any change is
made to an already assigned fsid).
3. Entries in the /etc/exports file are not necessarily file system roots. You may export multiple directories
within a file system. In the case of different directories of the same file system, the fsid should be the
same. For example, in the GPFS file system /gpfs, if two directories are exported (dir1 and dir2) the
entries may look like:
/gpfs/dir1 cluster1(rw,fsid=745)
/gpfs/dir2 cluster1(rw,fsid=745)
4. If a GPFS file system is exported from multiple nodes, the fsids should be the same on all nodes.
Large installations with hundreds of compute nodes and a few login or NFS exporting nodes require tuning
the GPFS parameters maxFilesToCache and maxStatCache with the mmchconfig command. The
Chapter 6. Managing GPFS access control lists and NFS export 53