Chapter 21.3.7, entitled "Externalize HTTP Sessions to JBoss Data Grid" makes bad recommendations for configuring distributed web sessions in conjunction with JDG.

1. There is no point to using a replicated-cache in conjunction with a write-through cache store. A replicated cache means that web sessions from all nodes are available in memory - thus the remote store would never end up getting utilized! To truly "externalize" web sessions to JDG, you would want to use an invalidation-cache. Otherwise, there is no point to using JDG at all.

2. The purpose of externalizing web sessions to JDG, is to handle more sessions than can fit in memory, without resorting to file I/O for passivation. Consequently, suggesting that users enable preload is a really bad idea, as this will force all sessions into memory of each node on startup.