Mixed Functions

When nodes act as both compute servers and PFS I/O servers, the same network bandwidth considerations discussed above apply. However, some performance gains may be realized by having a portion of the I/O operations access local disks. The likely limits of such gains are also discussed in "PFS and Storage Placement".

In order to maximize efficiency in the mixed-use mode, applications should be examined to determine the most efficient mapping of their processes onto cluster nodes. Then, the PFS file system should be set up to complement this placement with storage objects being installed on those nodes.

For example, a sixteen-process application may run best on a given cluster when four processes are scheduled onto each of four-CPU SMPs. In this case, the parallel file system should be configured with storage objects on each of the four SMPs.