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

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