Most services support either a worker or concurrency value in the settings. This allows the services to make effective use of the cores available. A good starting point to set the concurrency level for the proxy and storage services to 2 times the number of cores available. If more than one service is sharing a server, then some experimentation may be needed to find the best balance.
At Rackspace, our Proxy servers have dual quad core processors, giving us 8 cores. Our testing has shown 16 workers to be a pretty good balance when saturating a 10g network and gives good CPU utilization.
Our Storage servers all run together on the same servers. These servers have dual quad core processors, for 8 cores total. We run the Account, Container, and Object servers with 8 workers each. Most of the background jobs are run at a concurrency of 1, with the exception of the replicators which are run at a concurrency of 2.
The above configuration setting should be taken as suggestions and testing of configuration settings should be done to ensure best utilization of CPU, network connectivity, and disk I/O.
