This is done via JDBC module: http://publib.boulder.ibm.com/infocenter/bigins/v1r3/topic/com.ibm.swg.im.infosphere.biginsights.doc/doc/r0057924.html
They have the example for DB2.. just replace the connection string with Informix/JDBC connection string.. it will work.
There is even facility for parallel export/import. Some of these are not as automatic as they can be.
Of course, you're in map-reduce env...customization is needed for most tasks.