Upgrading 8.1 -> 9.x with ZFS rroot

[Gene]

Hi All:

I'm planning to move from my current FBSD 8.1 (amd64) to 9.2. My concern is 
that i'm using ZFS complete with a zfs root and I need to be sure that I don't 
manage to screw up that root. Can someone point me to some good reading on ths 
subject -

With grateful thanks,
Gene

And a Merry Christmas (or Happy Holidays) to all.

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