XI / PI in high availability setups

Did you install XI / PI in a high availability setup?
There is quite a bit of post processing needed to fully exploit these setups.
Look at the below SAP notes :
Note 1052984 - Process Integration 7.1 - High Availability
Note 951910 - NW2004s High Availability Usage Type PI

How To handle Backlog and Overload in XI/PI Systems

SAP has revised it's document on How To handle Backlog and Overload in XI/PI Systems and published it a few days ago. You can download version 2 of the document from Note 1045751.
It's a handy document and it can teach you more about how XI works.

Correct procedure to Stop/Start your XI system

The SAP Technical Operations Manual does not provide clear details on all the steps involved in stopping/starting your XI system. Now SAP released the details in Note 870864 and have updated the Technical Operations Manual with all the steps.

Import/Export Configuration Objects in XI

When you export/import XI configuration objects from one XI system to another you need to define transport targets in the SLD.See this SAP Help document : http://help.sap.com/saphelp_nw70/helpdata/en/ef/a21e3e0987760be10000000a114084/frameset.htm