Enabling and Configuring Disk Balancer

You can enable/disable disk space balancer and other settings using MCS and the CLI.

Enabling and Configuring Disk Balancer Using the MapR Control System

To enable and configure disk space balancer through MCS:

  1. Log in to MCS and click Admin > Clusters Settings > Balancer.
  2. Move the slider associated with Enabled to enable (Yes) or disable (No) disk space balancer and:
    • Proceed to step 3 if you enabled disk space balancer.
    • Skip to step 4 if you disabled disk space balancer.
    To enable disk space balancer from the command-line, see Configuring Disk Balancer Execution.
  3. Select one of the presets or specify a custom percentage for Threshold and Concurrent Disk Rebalancer settings. You can choose:
    • Disk Balancer Preset:
      Moderate (Default)
      • Threshold — 70%
      • Concurrent Disk Rebalancer — 10%
      Rapid
      • Threshold — 50%
      • Concurrent Disk Rebalancer — 5%
      Relaxed
      • Threshold — 90%
      • Concurrent Disk Rebalancer — 25%
    • Custom, use the slider to set the threshold and concurrent disk rebalancer percentages.
    Here:
    Threshold Specifies the minimum utilization threshold for a storage pool to become eligible for rebalancing. Default value is 70%.
    Concurrent Disk Rebalancer Specifies the maximum percentage of data that can be rebalanced. The cluster will wait until the number of rebalancing operations affects less than this percentage of total data eligible for rebalancing. The default value is 10%.
  4. Click Save Changes for the changes to take effect.

Enabling and Configuring Disk Balancer Using the CLI

The disk space balancer checks every storage pool on a regular basis and moves containers from a storage pool when that pool's utilization meets the following conditions:

  • The storage pool is over 70% full.
  • The storage pool's utilization exceeds the average utilization on the cluster by a specified threshold:
    • When the average cluster storage utilization is below 80%, the threshold is 10%.
    • When the average cluster storage utilization is below 90% but over 80%, the threshold is 3%.
    • When the average cluster storage utilization is below 94% but over 90%, the threshold is 2%.

You can use the config save command to modify disk space balancer parameter values.

Example: # maprcli config save -values {"cldb.balancer.disk.max.switches.in.nodes.percentage":"20"}

The following table lists the disk space balancer configuration parameters with their default values and descriptions:
Parameter Value Description
cldb.disk.balancer.enable 1

Specifies whether the disk space balancer runs:

  • 0 - Disabled (does not perform any container moves)
  • 1 - Enabled (normal operation)
By default, the disk balancer is disabled.
cldb.balancer.disk.threshold.percentage 70 Threshold for moving containers out of a given storage pool, expressed as utilization percentage. See also: Balancing Overused and Above Average Bins.
cldb.balancer.disk.max.switches.in.nodes.percentage 10 This can be used to throttle the disk balancer. If it is set to 10, the balancer will throttle the number of concurrent container moves (minimum 1) to 10% of the total nodes in the cluster rounded up. See Configuring Throttling.