Hi All, I was running hawq check on a system, and I hit the following error:
20160909:16:34:48:339941 gpcheck:hdw1:gpadmin-[ERROR]:-host(hdw1): on device (sdd) IO scheduler 'cfq' does not match expected value 'deadline' 20160909:16:34:48:339941 gpcheck:hdw1-[ERROR]:-host(hdw1): on device (sde) IO scheduler 'cfq' does not match expected value 'deadline' I did a bit of research, and generally I see hadoop hardware guides recommend cfq as the I/O scheduler, rather than deadline. http://amd-dev.wpengine.netdna-cdn.com/wordpress/media/2012/10/Hadoop_Tuning_Guide-Version5.pdf - Page 18 http://www.datanubes.com/mediac/HadoopTuningDHT.pdf - Page 9 Have we done any actual benchmarking for HAWQ I/O schedulers? Did we account for different use cases? Is deadline actually recommended for systems that run HAWQ, or is this recommendation just a holdover from the port from Greenplum? Thanks, Taylor Vesely
