I currently have 450 users that access an Exchange 2007 server that has the MB, CAS and HT roles on it. All MAPI and OWA connectivity for these users. Performance is very good for these clients. I will be adding another 1200 users and thus taking the CAS/HT roles and putting them on a seperate server. These 1200 users will be using Outlook Anywhere primarily. I would think the concurrency would be about 70% of those OA users connected at any given moment between the hours of 8:00 PM and 5:00 PM. Therefore do you think that several hundred OA users would put significant load on the CAS/HT server? I assume with enough RAM and beefy processor this should not really be an issue.Thanks,Alex

Alex,This would completely depend on the kind of transactions the users will do (You must have already noticed that in past). By the rule of a thumb I will always see the processor to memory ratio so that the server can accomodate more concurrent connections. Normally I use 1 GB per core of CPU for the CAS boxes but it will always vary depending on the connections at any given time. More the memory better is the performance. So ideally if I am selecting a server hardware for 1200 user, all using OA and connecting all at a time.. I will prefer 4 cores of CPU and 4 GB of memory if these users are not going to use emails heavily. But if you have heavy users in the organization who will be using OA you might want to consider increasing the memory upto 6-8 GB. Again, this recommendation will completely vary depending on the nature of users you have. Yet, you can try seeing few more recommendations here: http://msexchangegeek.com/2009/09/29/processor-and-memory-recommendations-for-exchange-2010/Milind Naphade | MCTS:M | http://www.msexchangegeek.com

Already answerd in Deploy Forum. :-)Milind Naphade | MCTS:M | http://www.msexchangegeek.com