Originally posted by pando
how big is your db

how many users are concurrently runing queries/transactions

I have never seen (so far in 4.5 years) a shop which uses windows to run mission critical apps such as CRM, Telecom Billing systems, DWH
Personal experience. It's a bank. Two instances on two-node Win2K cluster, Oracle FailSafe for HA purposes. Each instance has about 500-600 concurent sessions (dedicated server connections). Database size cca 300 GB each. One is transactional system, the other is DWH (kind of). Both are mission critical.