This section is dedicated to providing information on running NFS servers accessing GPFS file systems.
- Best Practices when running cNFS
- Using multiple interfaces in a cNFS node
- IBM Redbook: A Guide to the IBM Clustered Network File System
How do I:
- Configure the IP addresses used for cNFS file serving?
- Debug cNFS problems that are causing reboots?
Display the quota values of a fileset for NFS clients?
# chkconfig nfs off # chkconfig nfslock off # chkconfig rpcbind on
You can set up a cNFS server to serve two different subnets at the same time. cNFS understands multiple networks and ensures that the IP address is placed on the correct interface on start-up and during a fail-over event. For example if you have a Linux node with two interfaces for NFS connections:
You define the networks using mmchnode command
The GPFS cNFS code checks to see what interface (eth2 for example) an IP address should be assigned to. There are two ways to assign addresses for cNFS, you can use the device IP address or an alias.
Using the Device IP
Using an Alias
It is recommended that you use virtual IP addresses (an alias) instead of the interface address when configuring you IP address space for a CNFS cluster.
The advanatges of using Virual IP addresses include:
How to use an alias
To use an alias with cNFS you need to provide a static IP address that is not already defined as an alias (in the /etc/sysconfig/network-scripts directory). CNFS sets up the alias when it starts the interface So to set up an alias:
So why are my cnfs nodes rebooting? There are many reasons this could be happening:
By default when cNFS detects a failure (NFS, GPFS, OS etc) it reboots the server to attempt to recover from the failure. Sometimes to debug a node it may be useful to temporarily disable this feature. You can disable the automatic reboot by setting the cnfsreboot parameter.
It is recommended that reboot only be disabled when you are debugging a problem and you want to see the node in the failed state. Disabling reboot can cause IP failover to fail under some conditions.
GPFS supports the ability to set hard and soft quotas on a fileset. It is common to create a fileset in a GPFS file system that is then used as an export for NFS clients. When exporting a GPFS fileset you can configure GPFS such that when a NFS client issues the df command against the NFS mounted fileset they see the fileset hard quota level as the "Available" size instead of the space available in the entire file system. This feature is called filesetdf and is a GPFS file system configuration parameter. This allows you to utilize GPFS storage pools to share space amongst many different projects.
There are two steps required to enable the filesetdf feature for a file system.
To enable filesetdf for a filesystem use the mmchfs command. For example:
To disable filesetdf
The filesetdf setting can be changed while the file system is online.
This feature is available starting in GPFS 3.2.1-16 and 3.3.0-2.