Understanding Munin Output

I use Munin to monitor the health of our servers, I can tell by looking at the graphs there's nothing to worry about, however, I'm struggling to baseline acceptable performance.what would be classed as 'normal' output for some of the more relevant munin graphs.

I've been looking at the Apache* modules and this is the output from one of our servers:

average of: 300 accesses per minute, 6 busy servers and 4.10MB a minute volume

max of: 1400 accesses per minute, 81 busy servers and 51MB a minute volume

This is a dedicated box running one site.

We have another box that is running approximately 30 sites

average of: 30 accesses per minute, 1 busy server and a 500K a minute volume

max of: 322 accesses per minute, 11 busy servers and a 4MB a minute volume.

These servers are pretty much the same spec, dual core 64Bit, 4GB of ram, two SATA disks in RAID1.