in-situ conversion to FT disk config?

[Michael ODonnell]

>> perform an on-the-fly conversion from my vulnerable
>> single disk config to an FT config that brings that
>> second disk (hdc) into play without me needing to make
>> substantial changes to hda.
>
>No, that won't work; when you set up RAID or LVM on the
>disks, you'll lose all the data on the disks.

Understood.  I can dream, though...  theoretically it should be
possible to lay the {RAID,LVM,otherFT} metadata down on the disks
such that any existing {MBR,filesystem} bits remain untouched
and the disk becomes usable as part of an FT config (and maybe
even still being usable as a "normal" disk?)  DVZ's approach
does still require transfer of all data from the non-FT disk
to the newly config'd "degraded RAID" so you're right; it's
not a true in-situ conversion.  Still, it's a straightforward,
low-risk solution that doesn't require purchase of additional HW,
so I'm glad I asked.

> RAID protects you from a hardware failure; it's not a replacement
> for backups.

What?  well, if a RAID won't protect me against corruptions,
overwrites and the occasional "rm -rf *"   then, never mind!   ;->

Thanks for the feedback.