s7 redundant processor

Hi,
I am new to siemens system.I am working on a project .
here is the configuration in require.
Redundant CPU (Bumpless transfer)
redundant Power supply for each Redundant rack .
Distributed IO
HIM .
Please suggest me the best hardware for this.
As per my knoweledge it is only the S7-400 that supports hot backup of the cpu.I am not sure if s7-400 has redundant power supply.
I have very limited IO.totaling to 300 .

I would also like to know if there is Modbus communication module in Siemens.
My client requires an option for future integration with this system.
He needs MODBUS communication module . No AB PLC for this.
I hope to hear from you soon.

Scan.plc

redundant system : S7-400H(can be s7-300/400 if it is soft redundant system,above 315-2DP and SWR software)
MODBUS : CP341 + modbus dongle(it's double if you need redundant)
HMI : OP/TP + BUS REPEAT
Distributed IO : IM153-2 + i/o module

400H (High availability Model) is a fully redundant hardware solution. Fiber link between CPU's and I/O is accomplished via redundant Profibus networks. I/O cards can be Mono or dual type. Generally I/O is "Mono" and system takes care of the rest. Mono devices like VFD's, Starters and Instrumentation is achieved with Y-Link (Dual Profibus to Single).


300 Software solution is dual CPU's and linked over comm link (MPI or Ethernet usually). Everything as above except solution is Software based and requires a little more care and transfer times are longer.

In a nutshell the 400H solution is bulletproof and you treat the system like a single CPU. Download once and the system does the rest. For bigger systems or those requiring high performance this is the way.

Nick
http://www.automation.siemens.com/simatic/controller/html_76/produkte/produkte_hochverf_uebersicht.htm