by Joseph Stanfield
It is well understood that a server with a “balanced” memory configuration yields the best performance for your servers (See Memory Selection Guidelines for HPC and 11G PowerEdge Servers). Balanced implies that all memory channels of the server are populated equally and with identical memory modules (DIMMS). But there are certain situations where an unbalanced configuration might be needed. Cost limitations, capacity requirements, and application needs area all possible factors. This blog will provide a brief overview of how to gain the best performance from an unbalanced memory configuration.
To better understand the demerits of unbalanced configurations and to determine which unbalanced configuration is the best, several tests were conducted in our lab. We have seen many requests for servers configured with 48GB and 96GB of memory. Satisfying these capacity requirements on the latest generation of servers that have four memory channels per socket is only possible with unbalanced configurations. Using the available 2GB, 4GB, 8GB and 16GB DIMMs, we tested the configurations described below.