How to save log on Cisco switches-after restart I can't seeprevious events? Do I need Syslog server (how to configure), or can theswitch save log in its memory? I want to see what is going on in themoment when RPS start to supply switch. How to export this log int txtformat on local PC?

The switch can not save it's log after a reboot. You will need to send the logs to a syslog server. Here's a link on how to configure syslog. http://www.cisco.com/univercd/cc/td/doc/cisintwk/intsolns/as5xipmo/sysmgt.htm#xtocid4  Syslog is in plain-text readable format, so if you watch the events come in, you'll be able to read them real-time. Kiwi Syslog is a good choice.

Why RPS takes only one switch and notall six (they are advertising 750W), or am I doing something wrong.3750 has a way to config priority but all other switch are dependent onrps cable slot.

We use an RPS and it can only handle 2 3560 PoEs so I don't think it can handle that many 3750s. It also depends on the switch model and if it has PoE or not.

Hope that helps.

  I think you may have the wrong idea of what that 2300 does.  It is a backup power supply for devices  not a power redundant system.  It is there to keep the switch running if the internal power supply of a switch  dies. This gives you time to order a replacement .  To keep switches up in the event of a power failure you need a UPS backup system  to run the conventional power on the switches.  It is very unlikely you will ever have more than a single switch have a internal power supply failure at one time and this is the main function of that unit .

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps7148/ps7130/prod_qas0900aecd805bbf21.html