When using CodaHale Metrics in Java or Scala code a clustered environment what are the gotchas when reporting to Graphite?

If I have multiple instances of my application running and creating different metrics can Graphite cope - i.e. is reporting cumulative? 

For example if I have AppInstance A and B. If B has a gauge reporting 1.2 and another reporting 1.3 - what would be the result in Graphite? Will it be an average? or will one override the other. 

Are counters cumulative?

Are timers cumulative?

Or should I somehow give each instance some tag to differentiate different JVM instances?