Migrate existing RAID1 volumes to LVM on Proxmox

Question

Notes: I read How to convert SW MD RAID1 arrays to LVM mirrors? but wanted to pose the question as that is quite an old post. This is my first post.

I have a sw RAID1 (2 8TB HDDs that present to Windows Disk Management as Helthy, Mirrored) array with data on it that I want to preserve. This was originally configured with Intel Rapid Storage Technology. I currently don't have additional space to make a different backup.

The drives are in a newly installed Proxmox pve host machine that was set up with an ext4 LVM filesystem (Proxmox OS is installed on /dev/sda) that currently sees them as 2 separate volumes (/dev/sdc and /dev/sdd).

If I understand correctly, I should be able to take one of the drives and set it up as an LVM volume, and then add the data from the other drive to it. Next I would add the second drive to the volume group. Is this correct? If so, how would I do it?

Answer 1

Firstly, in a productive and professional system, you must have backup. Things sometimes die, thus they will die, and mirror does not defend you against accidental deletion. Nothing defends against accidental deletion, only backups.

Now go it further, so you don't have the backup. But you have the mirror, and you can use it as backup. By doing these steps, you risk accidental data loss, have backups, know what are you doing, no warranty, etc-etc.

Steps are these:

1. Detach one of the parts of the mirror.

2. Format that part as an LVM physical volume.

3. Create the logical volumes on it as you wish. Note, these must be dm-mirror volumes.

4. Copy the content from the now degraded more mirror into your LVM.

5. If everything is fine, reboot your system into your LVM.

6. Drop the remains of the RAID1, and reformat the second disk as an LVM physical volume.

7. Create the pairs of dm-mirror LVs and sync them.

I do not know if proxmox has any specific feature for that. Most likely it has not. If not, then you will need to do these from a rescue system. From the command line, yes you can do that, and this is what I would do in a professional setting (but only after I have created a full backup).