Hi,

C-JDBC (http://c-jdbc.objectweb.org) is an open source project that 
provides transparent database clustering to Java applications. From the 
application server point of view, it is just a regular JDBC driver. But 
underneath you have a Java middleware that provides replication 
techniques to achieve both performance scalability and fault tolerance 
using regular open source databases (in fact any database that provides 
a JDBC driver).
I think C-JDBC could contribute to Geronimo to offer an end-to-end 
clustering solution (having both clustering at the J2EE server level and 
also at the database level) using open source software on commodity 
hardware. No special effort should be necessary in Geronimo development 
to integrate C-JDBC since it interfaces with JDBC without requiring any 
application modification.

You can download both documentation and source or binaries from 
http://c-jdbc.objectweb.org/download.html. Let us know if you think that 
C-JDBC could be of interest for the Geronimo community.
Hope to hear from you soon,
Emmanuel