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Using software RAID only

Is it possible to start with a 2TB disk full of data and safely add it to a RAID 1 array?

Is it then possible to add a third disk and migrate the RAID 1 array into a RAID 5 array?


Is it possible to start with a 2 disk degraded RAID 5 array and then add the third disk later to create a health RAID 5 array?


I wish to migrate from a 2 disk NAS (RAID 1) to a 3 disk NAS and only purchase one new disk in doing so

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up vote 0 down vote accepted

You can convert a RAID 1 array into a RAID 5 array if you overwrite the RAID 1 metadata with RAID 5 metadata with mdadm. However, I have never done it nor would I try it without backing up all of my data. If I had a back up of all my data I would just wipe the disks, setup the RAID 5 and restore from back up instead of trying to convert a RAID 1 array into a RAID 5 array.

That said, I found an article that is kind of old but has the basic idea:

Use at your own risk.

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I have successfully done this in the past. It's been a few years, but one of things I love about mdadm is how versatile it is. No hardware raid I ran across would let me do something like this without doing a clean wipe + restore.

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