[GLLUG] Link two RAIDs in one LVM?

John Winters john at sinodun.org.uk
Mon May 11 20:16:54 UTC 2020

On 11/05/2020 20:14, Dr. Axel Stammler via GLLUG wrote:
> I feel rather nervous as I am about to do all this, and I do have some 
> questions (see below).
[snip detailed steps]

I wouldn't do it that way.  Possibly someone else can tell us a reason 
why it's worth moving the RAID functionality into LVM, but you don't 
need to, and given that your existing RAID is done with mdadm, I'd be 
inclined to stick with it.  It gives you less to have to undo.

My steps would be:

1. Create single large partition on each of the new HDDs.

2. Combine these into a new RAID1 device - mdN.

3. Give that device to LVM as its first Physical Volume, creating a 
Volume Group.

4. Create a single large Logical Volume, and then format that with 
whatever filing system you want to use - ext4 I think you said.

5. Copy files over with rsync as detailed previously.

6. Once you're sure you have all the files over, unmount the old filing 

7. Delete the old partitions on your old RAID1 device.

8. Add that RAID1 device to your Volume Group.

9. Enlarge your Logical Volume.


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