"This is also something that’s new to me, VMware is also doing intra-VM page sharing besides inter-VM page sharing"
(Via Yellow Bricks.)
Whoa! Now that is something that is obvious in hindsight, but absolutely astounding when you think about it. Lots of clients ask about the viability of virtualising Citrix servers on an ESX platform and there are a number of reasons why this can be useful like being able to easily clone servers to increase capacity and ensure that you get the exact configuration with all of the little tuning tweaks, avoiding some of the internal bottlenecks of Windows etc. However, this particular idea flew by under my radar. While inter-VM page sharing can result in some significant memory savings, a Citrix server has a whole lot of similar pages due to the fact that it's hosting a number of practically identical logon sessions. In hindsight it's obvious that ESX shouldn't care about the source of a give memory page when it does the shared memory consolidation. The net result is that you can run significantly more user sessions with the same amount of physical memory with Citrix running on ESX.