Number of nodes mounting the file system

The estimated number of nodes that will mount the file system may be specified at file system creation by using the -n option on the mmcrfs command or allowed to default to 32.

When creating a GPFS™ file system, over-estimate the number of nodes that will mount the file system. This input is used in the creation of GPFS data structures that are essential for achieving the maximum degree of parallelism in file system operations (see GPFS architecture). Although a larger estimate consumes a bit more memory, insufficient allocation of these data structures can limit the ability to process certain parallel requests efficiently, such as the allotment of disk space to a file. If you cannot predict the number of nodes, allow the default value to be applied. Specify a larger number if you expect to add nodes, but avoid wildly overestimating as this can affect buffer operations.

You can change the number of nodes using the -n option on the mmchfs command. Changing this value affects storage pools created after the value was set; so, for example, if you need to increase this value on a storage pool, you could change the value, create a new storage pool, and migrate the data from one pool to the other.