On 10.03.2015 01:23, Sam Varshavchik wrote: ...
For starters, in your case taking an existing partition and turning it into a RAID volume is going to be a big project. You'll have to back up your existing data somewhere, erase the existing partition, create a raid partition, then restore your data from backups. I'm not aware of a way to turn an existing non-RAID partition into a RAID one.
:)
man 8 mdadm
CREATE MODE ... To create a "degraded" array in which some devices are missing, simply give the word "missing" in place of a device name. This will cause mdadm to leave the corresponding slot in the array empty. ... For a RAID1 array, only one real device needs to be given. All of the others can be "missing".
"missing" == existing non RAID drive
In brief: 1. Create a "degraded" array with 2nd drive 2. Transfer the contents of the "missing" drive to it 3. Prepare "missing" and add it to the array i.e. RAID-1
Ref. There are plenty howtos out there.