Hello everyone,

Newbie here with a 4-bay system currently running single parity with two 4TB drives.

I would like to safely add in two 12TB drives which will:

• replace the parity

• Take the slots of the old drives (New drives into slot 1 and 2 and old drives will move to 3 and 4)

I have precleared both 12TB drives already and I’m ready to proceed with the safest way to do the swap.

I’ve read a bit on the parity swap procedure but I don’t think I understand fully, don’t want to risk data loss so any help is greatly appreciated.

Thanks!

You don't need parity swap.

New Config, assign disks exactly as you want, start array to begin parity build.

As I understand it,

1. Stop array

2. Move drives around physically

3. Restart array

4. Go to new config

5. Set preserve current assignments to all

6. Make new assignments

7. Start rebuild

   
   The old drives have data on it, this procedure keeps my info safe right?
   Thanks for your help
   

25 minutes ago, pilgrim said:

Set preserve current assignments to all

no, if you set this, you cannot make new assignments, it will keep the old config then.

actually it is

• stop array

• goto new config

• do NOT preserve current assinments (you could keep pools if you like, but NOT the array)

• put in new disks (the slots do not matter, so no need to move around all of them)

• make new assignments

• start array

• new parity will be generated automatically

Be cautious not to assign old data drive as parity, else content would be lost. But in your case you have to pick one of the 12Tb drives as parity, they are empty, so it does not matter

Edited November 29, 2025Nov 29 by MAM59

Thanks, what is the correct procedure in this case? I thought that’s what the first response from @trurl meant

read my msg again, i have updated it

Appreciate it! I’ll follow this

While the parity is being rebuilt, there will be no protection in this case right?

12 minutes ago, pilgrim said:

While the parity is being rebuilt, there will be no protection in this case right?

right, but the risk that a drive will fail during the parity build is small. 

Also, you surely have a backup, dont you? (parity is NO substitute for a backup!)

4 hours ago, MAM59 said:

if you set this, you cannot make new assignments, it will keep the old config then.

You can always make changes before you start the array whatever you preserve.

Thanks, I'm doing it now and hit a snag.

1. I stopped the array, powered it down and moved the disks physically.

2. turned it back on, it started the array automatically so I stopped it again.

3. Did a new config, preserved pools only

4. Back on Main tab, Ive assigned the drives as I want but cant start the array because of "Invalid expansion.: You may not add new disk(s) and also remove existing disk(s)."
   
   Not sure what to do now

That sounds as if you may have failed to hit the Apply button to actually execute the New Config (this is a not uncommon error). If it has been run correctly then the drives will have a blue icon when you return to the Main tab.

I think I only hit done, should I retry the new config?

6 minutes ago, pilgrim said:

I think I only hit done, should I retry the new config

not just retry, redo! :-)

Again, you have to set the check boxes for the things you wanna keep (pools?) then hit APPLY, then hit DONE

Repeated the step and it accepted my assignments, parity sync is now in progress. Appreciate everyone's help 🙏

good 😘

might have spoken too soon but the sync keeps changing to paused every few minutes. is this expected?

I pre cleared both new drives and had no errors, the existing drives also have been good and parity check was run regularly

think its the parity tuning plugin, turned off pause array operations for temperature changes. will see how it does now

The syslog should show whether the Parity Check plugin is pausing the sync (and why). You can turn off the options causing the pause in the plugins settings. If they are temperature related you could also set temperature related pauses to occur at a higher temperature than you currently have set.

Do you often have temperature problems during a normal parity check?

You should work on your cooling if so.

I've never had temp issues before, but these 12tb (avg 46 celsius) drives run hotter than my original 4tb (avg 37 celsius) ones. I will adjust the threshold, think I set my default values based on the cooler 4tb drives, unless these temps are actually high

Checked syslog and saw when the plugin paused the parity sync Parity Check Tuning: Paused Parity Sync/Data Rebuild (1.0% completed): Following drives overheated: parity(45C) disk1(48C)