Usually I recommend to set the global buffer (GB) as large as possible in order to maintain in memory more globals as possible. I don't know if this is a standard recommendation, but I want to discuss what should be the best buffer size for a Ensemble instance that only process messages.
I mean, if the instance only runs productions that pass messages then the 90% of the global access is used for persist the messages. In this situations a customer told me that he prefer to have a short global buffer because in this way the rest of the OS memory is available for use by the rest of the OS processes. He said that, for him, is more common to have a lot ot Ensemble jobs working and consuming memory but not intensive in the GB consumption. In this scenario if we set the GB too high then the system begin to swap memory pages to disk and this decrease performance. This happen because the GB is allocated from shared memory and this action is done at start getting the memory in an exclusive way.
I will thank any comment about memory setting for Ensemble productions. Pros and Cons, use cases, etc.