The HDFS balancer exits abnormally. The content of the pid file is not cleaned up, and the new balancer cannot be started.
Start the balancer (start-balancer.sh threshold 5)
Kill the balancer process (kill -9 <Balancer PID>)
Re-execute the balancer, there will be an error message.
– Balancer is running as process xxxx. Stop it first.
(But process already stopped, error message can be more detailed)