Thanks again drashna,
Yes, exactly. If you plug in/enable one or more the disks from "Pool B" in, it will recognize the disk, and even list the missing disks. As well as show the current contents, in a "Read Only" mode. Once they're all attached, it will list all the contents and set it back to "normal" (no longer read only).
I hoped that was what will happen.
So my current plan is to have 4x 2Tb in Pool A (file Duplication on), and have a Pool B 2x 2Tb (no file duplication), and Pool C 2x 2Tb (no file duplication).
And from time to time reattaching Pool B and Pool C alternatively to do flat filesyncs from Pool A.
Which means at any one time (even when backing up which will take a while sometimes - http://ResourceSpace,org multimedia stuff) there is one set of disks with the previous backup which is not attached electrically to anything.
Yes!
It was my friend's on the same properties LAN as we are on, and unfortunately he lost his computer as well..., the router and all the LAN hubs went crazy, and had to be completely powered off (dis-attached) for a few minutes each. Awesomely we had a virtualbox image of that machine, and backups of his recent database data to help him restore everything on a new Windows 8 pro hyper-v type setup.
A few years ago, another friend with more than adequate UPSes and even industrial strength spike protection over his whole his setup, lost absolutely everything throughout his complex (fax machines, phone routers, printers, the works).
So I am a great fan of off-line redundant backup!
Not at all paranoid, especially with original multimedia type material, it can even be irreplaceable, or very very expensive to get/shoot/photograph again.
We were blessed with a cheap, but very worthwhile, second hand fire-proof ( — probably EMF proof as well ), data-safe to put the backup hard-drives in, and may always have one set offsite completely!
Thanks again for the necessary information.
Paul