In exchange 2010 we do have 5 Server roles and the business logic build in middle tier, which means MAPI request goes to HLB ( if exists ), from there is goes to CAS Servers in Exchange 2010 Architecture, then the Exchange 2010 CAS start talking to Exchange 2010 MBX Server. The process in Exchange 2013 has changed, the business logic got moved into MBX Server role, while Exchange 2013 supports RPC/HTTP only dropping support for RPC/TCP. This means MAPI client will use RPC packets wrapped inside the HTTP to talk to their respected MBX Server.
Some of the compelling futures build into Exchange 2013……
- Exchange 2013 is much simpler to deploy , less servers roles, simple name space and better site resilience support.
- Exchange 2013 introduces huge cost saving by offering faster, and smarter messaging application.
- Exchange 2013 does have built in "application awareness" , new Exchange 2013 Application can detect and fix most of the problems automatically while the service continuity is not interrupted, ( much better seamless end user experience)
IOPS Reduction !!!!
This translate better performance obviously and cost saving, Faster the application is, better disk utilization and usage will be, allowing low end disk to be used and utilized by Exchange 2013.
Comparing exchange 2013 IOPS with some of the previous versions of Exchange Server
Exchange 2003---------------------------->95.5% IOPS reduction ( compare to Exchange 2013 )
Exchange 2010----------------------------->50-70% reduction in IOPS ( compare to Exchange 2013 )
|CAS||Client Access ( Available Role in Exchange 2013 )|
|HTS||Hub Transport ( Combined into CAS Role )|
|MBX||Mailbox ( Available Role in Exchange 2013 )|
|UM||Unified messaging ( Combined into CAS & MBX Roles)|
|EDGE||Edge Transport Server ( depreciated !!!! )|
In Exchange 2013 the Server Roles do have major reduction
|CAS||Client Access Server Role|
|MBX||Mailbox Server Role|
CAS Server Role
Domain joined Server ( not placed in DMZ ) existed within the ADDS name space. Provides Layer4 (transport) Load balancing
- Session affinity functionality got moved into CAS Server role.
- CAS Server Light weight protocol proxy Server
- Exchange Aware proxy Server, supports proxy and redirection
Here where you can find more information in regards to exchange 2013…