Performance Enhancements for SSD Based MapR-DB Deployments

For DB workloads on high-end servers, MapR has made several performance enhancements. For MapR-DB deployments on clusters with SSDs, two fileserver instances are configured on nodes with at least two SPs. On servers with SSDs, this feature is automatically enabled with a fresh install or upgrade.

Required Ports

Ensure that ports 5661 and 6661, as mentioned here, are open and available for this feature. To verify that these ports are open, run the following command from a remote machine:

/opt/mapr/server/mrconfig -i -h <ip> -p <port number> info threads

An error indicates that the port is not open.

NOTE: If you installed or upgraded to MapR 5.1 Enterprise Edition before opening the required ports, you can still enable this feature by opening the ports and restarting Warden on the node.

Determine Whether the Feature is Enabled

To determine whether this feature is enabled, run the following command:

/opt/mapr/server/mrconfig info instances

Your output will look similar to the following if this feature enabled. This output shows that two fileserver instances are running on ports 5660 and 5661.

# /opt/mapr/server/mrconfig info instances
2
5660 5661

Your output will look similar to the following if the feature is not enabled. It shows that one fileserver instance is running on port 5660.

# /opt/mapr/server/mrconfig info instances
1
5660

Disabling and Enabling the Feature

In certain cases, due to the nature of the workload, you may have to disable this feature. To disable:

  1. Run the maprcli config save command and set the value for the multimfs.numsps.perinstance parameter to a value greater than the number of SPs on any node in the cluster.

    For example:

    maprcli config save -values {multimfs.numsps.perinstance:500}
    NOTE: The default value for this parameter is 0. Changing this parameter can cause INSTANCE_MISMATCH_ALARM to be raised.
  2. Restart fileserver for the configuration changes to take effect and also clear any INSTANCE_MISMATCH_ALARM. To restart, run the following command: 
    maprcli node services -nodes <node name> -fileserver restart

If you reset the value for multimfs.numsps.perinstance to 0 or a low number (a number less than the number of SPs on the node), when Warden is restarted, this feature will be re-enabled and the SPs will be reassigned to 2 MFS instances.

NOTE: Changing this parameter can cause INSTANCE_MISMATCH_ALARM to be raised. Restart Warden to ensure that the number of instances run as configured.

Changes to Log Files

Additional log files are created in $MAPR_HOME/logs when this feature enabled. Please make a note of the following:

  • There will be two sets of log files, one per instance: mfs.log-<N> and mfs.log.<instanceID>-<N>, where <N> is greater than 0. For example:
    • mfs.log-3 for the primary instance
    • mfs.log.1-3 for the second instance
  • The RPC and security trace information is in these files: mfs.err and mfs-1.err.