On Tue, 27 Feb 2018 10:35:09 -0800, ultred ragnusen
wrote:

I've bought a new terabyte disk, and now have two terabyte disks side by
side (which I might RAID once I clean them out - but I never did RAID
before and googling finds that there are a LOT of up-front decisions to
make).


If you mean RAID 0 (striping), although it sounds like it should speed
up disk access, my experience is that it doesn't.

If you mean RAID 1 (mirroring), be aware that it is *not* a backup
solution. RAID 1 uses two or more drives, each a duplicate of the
others, to provide redundancy, not backup. It's used in situations
(almost always within corporations, not in homes) where any downtown
can't be tolerated, because the way it works is that if one drive
fails the other takes over seamlessly.

Although some people thing of RAID 1 as a backup technique, that is
*not* what it is, since it's subject to simultaneous loss of the
original and the mirror to many of the most common dangers threatening
your data--severe power glitches, nearby lightning strikes, virus
attacks, theft of the computer, etc. Most companies that use RAID 1
also have a strong external backup plan in place.

"Why RAID is (usually) a Terrible Idea"
http://www.pugetsystems.com/articles?&id=29