Damnit... I want to keep information on my peaks for capacity planning!
AVERAGE isn't the only archiving function you can use with rrdtool. For your purposes, you should create an additional RRA with an archiving function of MAX. http://oss.oetiker.ch/rrdtool/doc/rrdcreate.en.html#IRRA_CF_cf_arguments
If for each object o1 of type S there is an object o2 of type T such that for all programs P defined in terms of T, the behavior of P is unchanged when o1 is substituted for o2 then S is a subtype of T
which, when stated in the words of Robert "Uncle Bob" Martin as something we probably all intuitively understand from our daily work, is:
Functions that use pointers or references to base classes must be able to use objects of derived classes without knowing it
Saliva causes cancer, but only if swallowed in small amounts over a long period of time. -- George Carlin