Hey folks

First timer here. I bought three WD Red plus 8TB HDDs for my server. Was following the setup guidelines but for some reason, one of the disks always fails to mount in the array. No matter how many times I start the array and click on the 'Format' button, it always instantly fails with the error 'Unmountable: unsupported or no file system'. The logs show the following error: `root: mount: /mnt/disk1: wrong fs type, bad option, bad superblock on /dev/md1p1, missing codepage or helper program, or other error.`

Things I've tried so far:
1) Different array configs like 2 data + 1 parity array, 2 data array, 1 data array but all the configs still had the same disk fail mounting in unraid.

2) Wipe and format through cmdline, as mentioned in https://forums.unraid.net/topic/181021-cannot-format-new-disk-to-createadd-array/. I did not run a full dd however.

3) Wipe and format multiple times through Unassigned Devices plugin.

4) Couldn't try check in the disk menu after starting in maintenance mode. It doesn't even show up there. Attached a screenshot for this.

I've attached the diagnostics from a new config with only this disk in the array. This doesn't seem like a hardware issue as I'm able to mount the drive using Unassigned Devices plugin and am able to browse through the contents (the disk is empty though). Any help would be gladly appreciated here. Thank you in advance!

diagnostics-20251215-1821.zip

The "normal" way to add a new disk would be just to:

• stop the array

• add the drive to the array list

• can't start the array because of the new drive

• but NOW there is a new button (actually 2) on the array start page!

• select the new disk from the list and check the checkmark box ("I really want this!")

• Done!

The thing is, a new disk never has a proper filesystem and therefor needs to be formatted.

Hint: check the disks settings before to set the filesystem type!!! Currently your disk has "auto" which means: "if there is already a filesystem on the drive determine which and try to mount it, else use the type from the global Disks Settings".

Once acknowledged the disk will be formatted, mounted and the array started.

(Sorry, no screenshot. these buttons only appear after you have added a new drive)

Edited December 16, 2025Dec 16 by MAM59

Dec 15 18:19:54 dEagle emhttpd: shcmd (1787): mkfs.xfs -K -f -m crc=1,finobt=1 /dev/md1p1

Dec 15 18:19:54 dEagle root: size 4091 of data subvolume is too small, minimum 4096 blocks

Disk1 has an existing very small partition. Since there's no parity, you can do a new config (Tools - New config - Keep all - apply) then go back to main, lcik on that disk and then "Erase", then start the array and format it.

Thanks for the suggestions. I re-plugged the cables again and the drive got mounted magically with first boot.