Thanks for the reply Rich, unfortunately we are stuck with the IRIS driver which does work fine for normal ODBC and Linked Server DSN. I was hoping someone had gotten Polybase working specifically with an IRIS driver but doesnt sound like it yet.

Hi Kurt, would you mind sharing the External DataSource creation code you used to connect to Cache? I am trying to do the same thing and getting a similar error on External Table Creation "Driver Not Capable". I'm just trying to pull in one column for testing and its a simple varchar(20). Native Error 469 doesnt tell me anything when I look it up other than Driver Not Capable. We recently upgraded to the IRIS drivers and they work for linked server without issues.  Any help would be appreciated.