***Update for anybody reading this later on***

So, as it turns out, Clearing the disks in Unraid, doesn't remove all of the partitions. In my case, these were drives that were previously in my Synology NAS, so they had multiple partitions. If you are planning to add drives that have been used in another device, always check them with Unassigned Devices first to see what partitions they have. You will want to remove those before adding them to your Array so you can actually use the whole disk.

If you're in the position I was, check out JorgeB's steps toward the end of this post. I did this and was back up and running no problem.

Hey all,

I had an Array with 1 Parity and 4 Data Disks. My previous config was:

20tb - Parity

20tb - Data

8tb - Data

8tb - Data

8tb - Data

I added 3 disks to the Array, but for some reason all of the new disks are appearing as 8tb. It seems like they're defaulting to the smallest sized disk in my current Array for some reason. The used space reported looks pretty crazy too. These are tested and working drives.

Since these are showing as 8tb and are below the 8tbs above them, I wondered if the order of my disks mattered for whatever reason? Other than that I'm not really sure why these would be reporting incorrectly like this.

Steps I've taken:

• Checked Filesystem Status on all drives. All show good.

Any help would be appreciated. Thanks!

Edited September 11, 2025Sep 11 by Skarm0ry

That suggests they had an existing smaller partition; please post the diagnostics to confirm.

Hi @JorgeB

Here is my Diagnostics file. Let me know if there is anything else I can provide.

A little more context on these drives. They were previously used in a Synology NAS, so they were not being used at full capacity. I didn't think that would matter after a clear and format, but figured I'd mention that as well.

One other thing to note is, there is no data on any of these 3 disks, so I'm fine with completely clearing them some other way if that is an option. I assumed the clear/format did that, but I guess not.

Edited September 11, 2025Sep 11 by Skarm0ry

As suspected, they have multiple partitions, and Unraid uses the largest one:

Sep 11 08:35:03 Tartarus emhttpd: disk sdj 12000138625024

Sep 11 08:35:03 Tartarus emhttpd: part sdj1 8192 8589934592

Sep 11 08:35:03 Tartarus emhttpd: part sdj2 16785408 2147483648

Sep 11 08:35:03 Tartarus emhttpd: part sdj5 21257952 7990579855360

Sep 11 08:35:03 Tartarus emhttpd: part sdj6 15627875328 3998563581952

There are two options: rebuild the disks one at a time, Unraid will recreate the partitions, or manually wipe the disks and then rebuild parity, any doubts, please ask first.

Hi @JorgeB

Thanks for the reply. I'd probably prefer not to do the rebuild one at a time since that will take a week or so. I'd probably prefer to manually wipe and rebuild parity after. So knowing that I'd just like to confirm my steps.

• Remove 3 new Disks from Array

• Use Unassigned Devices + to do a destructive format on each of the drives

• Add drives back to the Array

• Rebuild Parity after

Since the original disks from the array are the only ones with data, there really should be no risk of data loss here right? When removing and re-adding the drives, do I just do that from the Main tab in the Dashboard, or do I need to do anything in Tools -> New Config?

You do not need to format the drives in UD (although it will not do any harm). Make sure, though that in UD you first remove the existing partitions.

The easiest way is:

• Tools - New config - keep all - apply

• Click on disk5 - Erase disk

• Click on disk6 - Erase disk

• Click on disk7 - Erase disk

• Start array to begin parity sync

• Click format to format those 3 disks (can be done during the sync).

And now we wait. Drives look now. No idea why the initial Clear on the drives didn't remove those partitions, but I'll keep an eye out for that from now on.

Thanks for the help!

Just now, Skarm0ry said:

No idea why the initial Clear on the drives didn't remove those partitions,

Unfortunately, that's a limitation of how the Unraid driver works, and the order things are done, I've asked LT if it was possible to always wipe new disks, but it's not a simple thing to change.