For several years I've had a 12TB disc that I used as an unassigned device that I would backup to and store in a gun safe. I got close to filling up the disc so I bought a small 2 disc RAID 0 device and a matching 12TB disc. I added the new 12TB drive to the RAID 0 box. I ran PreClear and after 66 hours the PreClear finished.

I'm not finding an option to format the discs. In the error log it looks like UnRaid sees one of the drives and the wording makes me think what I'm trying to do is not going to work.

My question is can I combine the 2 matching discs in this manor as a RAID 0 disc and present them to UnRaid in the form of an unassigned device that's a 24TB disc?

Thank you for the help.

Problem look like because you only insert one disk in RAID0 box, to be support form a 24TB disk, this really depends on the box support or not.

But why don't simple create a RAID0 pool and mount that by UD, the only reason I expect is lack of SATA / SAS port. Not recommend use RAID box, you probably will loss disk health status monitoring.

Edited July 29, 2025Jul 29 by Vr2Io

I understand you to say - I would be better to build a RAID 0 Pool in UnRaid using my two 12 TB Discs to build the Pool. Correct

No, if it's an offline backup it should stay unassigned. Pools are not meant to be removed.

What are the drives and enclosure, and what does unraid see? If it is a RAID box and is configured correctly Unraid should only see one single drive as unassigned device.

Both Drives are Western Digital 12TB WD120EFBX. The enclosure is a Mediasonic HUR5-SU31C, it is a 2 disc device with Single, JBOD, RAID 0/1 functions. I have it in the RAID 0 setting so I can get the total 24TB of space. I named it "24TB_Backup_Disk".

The IDENTIFICATION column is showing the serial number of the original 12TB Disc that I was backing my "/plexmedia/movies" Share successfully to with RSYNC using this command ->

"rsync -avh --delete "/mnt/user/plexmedia/movies/" "/mnt/disks/12TB_Backup_Disk/movies/""

I added the 2nd 12TB disc and did a PreClear. After the PreClear UnRaid does show the Size to be 24TB

The "Mount" button is Greyed out.

This is the log file:

I can't figure out how to do the Format to make the drives be seen, which is why I think the "Mount" button is Greyed out.

Thank you for your response Kilrah

If you click "X" to clear disk, then UD could create the filesystem success ? After that it just grey out the mount button ? Pls provide the message / log as above.

Pls also try " wipefs -f /dev/sda ".

1) I'll try the " wipefs -f /dev/sda " first and give that feedback as well. If that doesn't help I'll got to your suggestion, below.

2) I did think about clicking the "X", but when I do it tells me it's going to force the PreClear again. It took almost 67 hours the first time. I've never tried, but maybe the answer to that is to Stop the PreClear once it starts so I don't go through that again. The discs did pass when I already ran it, so they should be good. Can you give me feedback on that assumption. If that has a good chance of working I can try it.

Thank you Vr2lo.

2 minutes ago, barryfjohnson said:

2) I did think about clicking the "X", but when I do it tells me it's going to force the PreClear again. It took almost 67 hours the first time. I've never tried, but maybe the answer to that is to Stop the PreClear once it starts so I don't go through that again. The discs did pass when I already ran it, so they should be good. Can you give me feedback on that assumption. If that has a good chance of working I can try it.

I haven't preclear disk longtime, this seems UD / preclear associate together, for me, if I click "X" it won't preclear disk, (I haven't install preclear plugin). You may try uninstall Preclear disk plugin.

I always use Wipefs, simple and seems deep clean little bit.

Edited July 30, 2025Jul 30 by Vr2Io

I will try 1) then uninstalling PreClear and see if 2) works.

Thank you...

5 hours ago, barryfjohnson said:

2) I did think about clicking the "X", but when I do it tells me it's going to force the PreClear again. It took almost 67 hours the first time.

There is no need/point for preclearing for an unassigned device, it's only relevant for a drive that you will add to the array.

So yeah click the X then format.

I ran the "wipefs -f /dev/sda", it didn't seem to do anything.

I removed the PreClear app.

I clicked the red "X" and the RAID device with the 2 disks had some activity. Here is the log file and what UnRaid shows now.

I'm going to try clicking on the "FORMAT" button (crossing my fingers of course). I do another post to tell what happens.

I think Formatting with BTRFS would make the external RAID more compatible with Windows 10. I can see a use case where I would like to connect that device directly to my Windows 10 PC to copy files.

So, if one of you can tell me your advice, I'll not do the Format until I hear back. XFS or BTRFS ?

Currently, all the discs that make up the Array are "XFS" the Cache drives (2) are BTRFS.

I am not sue does BTRFS does perfect access on Windows (install proper SW), I use BTRFS always.

You can made some test for final decision, clear and format disk just on the fly usually.

Edited July 31, 2025Jul 31 by Vr2Io

BTRFS is said to produce trouble, USB connected drives are said to produce trouble.

Together they may give double-trouble... keep this in mind.

Note that there is also an "OpenZFS" version for windows in the development. It is usable already and it can mount UNRAID zfs disks (at least single ones) for now.

So a ZFS formatted drive can also be used on Windows directly now.

If you want to mount on Windows the best choices would be NTFS or ExFAT, but they'll have the disadvantage of not supporting linux file permissions depending on what you want to put on there.

Before I commit to formatting my 24TB disc, I'm going to try different formatting on a much smaller disk to see how my idea works out.

I still have the unknown if the 24TB disk in the little RAID 0 box is going to work anyway, no matter which file system I use to format it with.

More to follow...

Just as an update. I stuck a 2TB disk as an UD and formatted it as NTFS. I copied 80 files over to the disk using RSYNC.

Once the copy finished, I unmounted the disk and plugged it into a WIN10 PC. I was able to read the files without issue.

I formatted the 24TB disk and started a copy of almost TB using RSYNC. It's 8:40 right now and there have been 2.65TB copied so far.

More to follow...

Sorry there are about 11TB total to copy to the new 24TB RAID 0 array in the external box.

The backup finished without issue. I unmounted the disk and moved it to my Windows PC. I validated the data (1941 Movies) was good.

I appreciate all the good advice, as usual when I do a UnRaid project, I learn a lot.

Thank you!