[CentOS] MegaRAID, and creating a RAID 1 while live

Wed Apr 10 17:41:42 UTC 2019
mark <m.roth at 5-cent.us>

I've started searching, but if anyone here has a link.... I *just*
discovered yesterday, to my dismay, that a previous admin built a box that
has four hot-swap bays as two as RAID 1... and the other two as RAID 0.

Honest, I thought I was pulling the failing drive out of a RAID 1, not
that the RAID 0 contained all the websites for a production box....

So, what I want to do is this: it's a Dell, with a PERC 710. Let's call
the two drives I'm dealing with sdb and sdc. With mdadm, what I'd do is
1. copy what's on the the RAID 0 of sdc to the RAID 0 of sdb,
2. create sdc as RAID 1, with a drive missing.
3. copy everything from sdb to sdc, and finally.
4. kill the RAID 0 of sdb, and add it as the missing drive to the new RAID 1.

And, all with MegaCli64....