First of all, awesome back up program.  I love the flexibility and power! 

I was curious as to back up routines you all were running on a medium (~40 client set up) sized network.

I am starting with a 750 GB drive (mirrored with raid 1).  I have done some tests with clients and most full backups are less then 5gig...most actually being half that and some way more. 
I have tried my best to use all the variables backuppc offers and looked into funky arrays, but need some other insights! 

I was thinking full backups every 30 days, incrementals every night... but wasn't sure how efficient that would be and quite frankly it seems too easy

Any suggestions of variables are welcome :)  thanks!

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Lyle Scott, III
http://www.lylescott.ws