Hi, if the mapred.max.split.size is not set (and it's not by default) than CombineFileInputFormat only takes racks in account when grouping blocks. So if you set this property it will take also block placement on machines into account and you should get multiple mappers.
Hope this helps, Aleksandar Stupar. ________________________________ From: Keith Wiley <kwi...@keithwiley.com> To: common-user@hadoop.apache.org Sent: Thu, April 29, 2010 11:23:35 PM Subject: CombineFileInputFormat not producing multiple mappers I am using CombineFileInputFormat and CombineFileSplit to group small input files as fed to the mappers. The job runs properly and the output is correct, but I get only one mapper task, so I lose all my paralleization in the map stage. I realize I'm not providing much detail yet because I'm not sure what to say. Feel free to ask questions for clarification. What might cause this problem and how might I diagnose -- must less fix -- it? Thank you. ________________________________________________________________________________ Keith Wiley kwi...@keithwiley.com www.keithwiley.com "And what if we picked the wrong religion? Every week, we're just making God madder and madder!" -- Homer Simpson ________________________________________________________________________________