Nodes

Configuring a Sun SMP or cluster of SMPs for Sun HPC Software use involves many of the same choices seen when configuring general-purpose compute servers. Common issues include the number of CPUs per machine, the amount of installed memory, and the amount of disk space reserved for swapping.

Because the characteristics of the particular applications to be run on any given Sun HPC cluster have such a large effect on the optimal settings of these parameters, the following discussion is necessarily general in nature.

Number of CPUs

Since Sun MPI programs can be run efficiently on a single SMP, it can be advantageous to have at least as many CPUs as there are processes used by the applications running on the cluster. This is not a necessary condition since Sun MPI applications can be run across multiple nodes in a cluster, but for applications with very large interprocess communication requirements, running on a single SMP may result in significant performance gains.

Memory

Generally, the amount of installed memory should be proportional to the number of CPUs in the cluster, although the exact amount depends significantly on the particulars of the target application mix.

For example, at a minimum, a Sun Ultra HPC 2 (two-processor) system should have 256 MBytes of memory.

Generally speaking, computationally intensive Sun HPC applications that process data with some amount of locality of access often benefit from larger external caches on their processor modules. Large cache capacity allows data to be kept closer to the processor for longer periods of time.

Swap Space

Because Sun HPC applications are, on average, larger than those typically run on compute servers, the swap space allocated to Sun HPC clusters should be correspondingly larger. The amount of swap should be proportional to the number of CPUs and to the amount of installed memory. Additional swap should be configured to act as backing store for the shared memory communication areas used by Sun HPC ClusterTools 3.0 software in these situations.

Sun MPI jobs require large amounts of swap space for shared memory files. The sizes of shared memory files scale in stepwise fashion, rather than linearly. For example, a two-process job (with both processes running within the same SMP) requires shared memory files of approximately 35 Mbytes. A 16-process job (all processes running within the same SMP) requires shared memory files of approximately 85 Mbytes. A 256-process job (all processes running within the same SMP) requires shared memory files of approximately 210 Mbytes.