At TechEd, Microsoft said that its upcoming Exchange Server 2010 currently in beta, software will be able to read and write e-mails to disk 70% faster than Exchange 2007, despite the fact it uses the same database engine. All address performance and scalablity, which has long been a sore point for Exchange administrators and users, with Exchange's Jet database engine taking much of the blame. While keeping Jet for Exchange 2010, Microsoft changed its storage schema such that reading and writing mails to disk will be smoother and less bursty. That will result in a 70% I/O improvement over Exchange 2007, and 90% improvement over Exchange 2003. Exchange 2010 mailboxes will also be able to store up to 100,000 items per folder, up from 20,000 in Exchange 2007 and 5,000 in 2003, said Ross Smith IV.
More info: ComputerWorld