You can use ps to monitor the database and Spread processes running on each node in the cluster. For example:
$ ps aux | grep /opt/Vertica/bin/Vertica
$ ps aux | grep /opt/Vertica/sbin/spread
You should see exactly one Vertica process and exactly one Spread process on each node. To monitor Administration Tools and connector processes:
$ ps aux | grep Vertica
There may be many connection processes but at most one Administration Tools process.