Criteria for Reduce Slot Calculation

MapR Hadoop sets the number of reduce slots to the lowest value that results from the following memory, CPU, and disk calculations:

• Memory calculation = (0.6* memory available to process MapReduce v1 tasks)/ memory for allocated to each reduce task
• CPU calculation:
  • If # CPUs on the node > 2, then the CPU calculation is = number of CPUs on the node – the number of CPU assigned to MapR-FS Note: The number of CPU available to the MapR-FS is 4 for an Enterprise Database Edition installation. Otherwise, the value is 2.
  • If # CPUs on the node <= 2, the CPU calculation is = 1
• Disk calculation:
  • If the # of disks available to the MapR-FS > 2, the disk calculation = 0.75 * the number of disks available to MapR-FS
  • If the # of disks available to the MapR-FS <= 2, the disk calculation = 1