(1) Pending internal events and or reconciliation events count are increasing and the BBAS-AS logs are growing abnormally large Snip: One potential cause could be a failure in communication between multiple BlackBerry Administration Service nodes. Source: KB25726-Pending internal events and or reconciliation events count are increasing and the BBAS-AS logs are growing abnormally large (2) Performance considerations for the BlackBerry Administration Service
RIM recommends these:
(1) Maximum of 4 BAS nodes in a pool
(2) No latency of > 20ms for network communication between BAS node and SQL server. Snip1: Due to current limitations, it is recommended to have not more than four BlackBerry Administration Service nodes in the pool. Snip2: To maximize the performance of the BlackBerry Administration Service and avoid slow response times, computers that host the BlackBerry Administration Service should be placed in the same data center as the Microsoft® SQL Server® that hosts the BlackBerry Configuration Database. Round-trip latency should be less than 20 milliseconds. Source: KB24632-Performance considerations for the BlackBerry Administration Service Remarks:
Above are just guideline IMHO as each environment differs. The thumb of rule is the lesser the latency between the communicating components the better performance. Although there is no RIM guideline on the latency between BAS nodes, as I mentioned the lesser the latency the merrier your BES will be.