TAPE BLOCK SIZE

I am running tbtape from UNIX 3.2 and Informix 5.X engine on IBM RS6000. I have a 10GB database and am using 5.0 GB IBM 8MM Tape Drive. It takes 4 hours to do a back up. We are using a blocking of 20 in the Informix Configuration and the tape block size is set to 20480. I have changed this to 240 for the Informix Configuration and 245760 for the tape drive. I then got a to 3 hours. So smart me changed it to 960 hoping it would at least get to 2 hours, if not one. BUT NO It went back to 4 and used more tapes. Anyway my question is does anyone know a MAGICAL set of tape drive and configuration numbers that I could try to get this archive to process in at least 2 hours? If you do please let me know. I and the operators would love it if we could cut our archive down to 1/2 the time. THANKS IN ADVANCE!!!!!!!!!!!!!!!!!!!!!!! ------------------------------------------------------------------------- Cheryl Kendricks Internet: cherylk@spamis.jcdc.doleta.gov OR cherylk@prod1.jcdc.doleta.gov OR kendric@gwysmtp.jcdc.doleta.gov DTSI, Inc. Voice: 1-800-598-5008 Database Administrator - DOL Job Corps San Marcos, Texas ------------------------------------------------------------------------