Hello all,
I am running a 4-nodes CDH5 cluster on Amazon EC2 . The instances used are
m1.large, so I have 4 cores (2 core x 2 unit) per node. My HBase table has
8 regions, so I expected at least 8 (if not 16) mapper tasks to run
simultaneously. However, only 7 are running and 1 is waiting for an empty
slot. Why this surprising number came up? I have checked that the regions
are equally distributed on the region servers (2 per node).
My properties in the job:
Configuration mapReduceConfiguration = HBaseConfiguration.create();
mapReduceConfiguration.set("hbase.client.max.perregion.tasks", "4");
mapReduceConfiguration.set("mapreduce.tasktracker.map.tasks.maximum", "16");
My properties in the CDH:
yarn.scheduler.minimum-allocation-vcores = 1
yarn.scheduler.maximum-allocation-vcores = 4
Do I miss some property? Please share your experience.
Best regards
Tomasz
