The following reasons are cited by Siddarth Waggle in AMBARI-5707 (https://issues.apache.org/jira/browse/AMBARI-5707) as reasons for the proposal of Ambari Metrics:
Problems with current system:
- Ganglia has limited capabilities for analyzing historic data, new plugins are not easy to write.
- Horizontal scale out for large clusters.
- No support for adhoc queries.
- Not easy to add metrics support for new services added to the stack.
- It is non trivial to hook up existing time series databases like OpenTSDB to store raw data forever.
There was also a number of customers already using Nagios and/or Ganglia in their infrastructure and there were version incompatibilities between those installations and the versions shipped with HDP.