Does decreasing the interval of checks require recreating the rrd files?

[Charles Jones]

Subject pretty much says it all.  If I want a more granular graphs, 
which checks done and graphed every 2 minutes instead of the default 5, 
what all do I have to change?

I'm also being asked that...if the hobbit interval is currently every 5 
minutes, are client-reported alerts sent out instantly (as soon as they 
are received), or are they only processed during the update interval. 
For some very critical services, waiting 5 minutes to find out that it's 
down can be too long.

Thanks,
-Charles