Hi,

I'm using an small setup with two Westerd Digital WD Blue 2Tb disks, one as parity and the other as data disk. Recently the WD Blue assigned as data disk has failed, leaving me with only the parity WD Blue disk working.

While planning the disk replacement, I've read that a Western Digital Blue is a SMR drive which is NOT recommended for parity. Therefore, I've bought to replace the faulty disk a Western Digital Red Plus 2Tb which is a CMR drive type, most appropriated to serve as a parity drive.

Now I need to use my working WD Blue as disk, and place the new WD Red Plus as parity.

I thought about two plans for that:

Plan A (I think it is going to fail because I would use the dual parity to create a new parity disk which would be later again single parity):

1. Install the new WD Red Plus as a secondary parity (which is not going to clone the first parity)

2. Clear the old WD Blue which was serving as parity and use it as a data disk

Plan B (This might work better but I would like to check)

1. Clone the current WD Blue serving as parity to the WD Red Plus (ddrescue -f /dev/sdX /dev/sdY /boot/ddrescue.log)

2. Clear the previous WD Blue which was serving as parity

3. Configure the clonned WD Red Plus as parity and the WD Blue as data

4. Start the array to rebuild the WD Blue data using WD Red Plus as parity

What do you think? Thank you!

Edited December 5, 2025Dec 5 by rodtin

In what way did the data disk fail?

Attach Diagnostics ZIP to your NEXT post in this thread, preferably with the failed disk attached.

Hi trurl,

When I've connected the new WD Red disk I've realized that it was failing as well so the problem was not the WD Blue but the controller itself.

I've changed the controller and now I have all disks working being two WD Blue (one as parity and one as data) and a new unassigned WD Red. All of them working fine (complete SMART tests passed for all disks), rebuild done and parity verified.

However I still would like to use the WD Red as parity, what would be the best plan to do this WD Blue -> WD Red parity swap?

Br

If you do not mind ending up with parity2 and no parity1 then the easiest would be.

• assign WD red as parity2, and then start array to build parity2.

• When that completes successfully stop array

• Unassign parity1

• Start array to commit change

At thi s point you can use the old WD Blue as a data drive.