How to backup a Time Machine backup

How can I best backup a Time Machine volume?
After a house fire that luckily didn't reach the computers, I was thankful that I did have backups so could be sure it wasn't a data disaster, but it got me thinking. The server providing the TM volume is in the same room as the Macs being backed up and if the fire had entered that room, all would have been toast, backups and all. So I want to setup an 'off-site' backup to avoid this potential problem. In fact, it will be another Mac in a nearby but separate building and I want that to keep a copy of the Time Machine volume. In fact it really wants to be a mirror of the TM volume so it could be used as the TM volume instead of the original (which would of course be unusable, hence the need to use the backup).
Since all TM backups are across the network, each client Mac has its own large backup file and any backup program that simply checks modification dates would therefore copy the files across every time as they would have changed, whereas Time Machine itself would only be copying a few changes each time.
Anyone any bright ideas about the best way to implement such a backup copy of a Time Machine backup volume?


I have a question along the same lines and it might be of help to the author of this thread.
What about a Time machine RAID?
I am thinking about upgrading my 24" iMac to a 27" with much larger 2TB HDD. My current machine has a 500 GB. I back up to two WD MyBook Studio 500 GB drives which I have partitioned. One partition is for TM archives (which is my understanding of what TM makes: additive incremental archives) and the other partition is for weekly bootable duplicates I make with Carbon Copy Cloner.
I rotate one drive off site every week just in case of the dreaded house fire.
This set up seems to work okay in that I have two sets of backups, with one off-site at all times. The most data I stand to lose is one week, since I switch my backups every Monday.
However, the only drawback is that the Time Machine archives are not the same. They both contain the original TM back up I did way back when I first set up the drives, but since I am rotating the drives off site every week, they contain staggered back ups from thence forward. If I go to look for a file that I only had on my computer for one week and later deleted, that file will only exist on one TM drive and not the other.
So, long story short, a three disk RAID seems to be the best way to achieve TM back ups that are identical. Two drives would be constantly connected to the computer with the third drive rotating off site.
However, I have read on other threads that people were having problems using TM with a RAID set up.
Does Time Machine play well with RAIDs? Is there a particular RAID set up I should use? Can I partition the RAID in order to separate my TM archives from my bootable duplicates? Will the machine boot from a duplicate stored on a RAID?
Forgive all the monotonous questions, but I have never set up a RAID before so I am a total novice.