Backup questions (TM, CCC + CrashPlan)

Looking for advice on my backup strategy. I have an iMac that I use for my main day to day. It's connected to a 16tb RAID 5 array, where all of my original data sits. Connected to it is a 20tb RAID 5 array. I use Time Machine to backup everything on my 16tb to the 20TB. I use Carbon Copy Cloner to copy everything from my 16tb to my 20tb. I use CrashPlan to backup everything on my iMac and my 16tb primary. Every six months, I take the most recent data and put it onto an external drive for vault storage in my garage.

1. Is this overkill?
2. Time Machine gave me a full warning today for the first time. I have it pointed to my 20tb drive.

Thanks.