Hi all,

I have a disabled data disk (Disk 3) that I cannot re-enable due to a ghost Parity 2 slot (slot 29) in my superblock keeping mdNumDisabled=2. The UI never offers a Recover or Re-enable option because of this.

System:

• Unraid 7.3.1

• LSI SAS2008 HBA (new replacement)

• 4x Seagate Exos X20 20TB in array (BTRFS)

• Disk 3 serial: ST20000NM007D-3DJ103_ZVT64229

The problem:
Disk 3 went disabled after what appears to have been a backplane connection issue. SMART on Disk 3 is completely clean — no reallocated sectors, no pending sectors, no uncorrectable errors. The filesystem is intact and mounted.

However there is a ghost Parity 2 slot (slot 29 internally) that is permanently stuck as DISK_NP_DSBL. This keeps mdNumDisabled=2, which prevents Unraid from offering any re-enable or rebuild option for Disk 3.

Diagnostics:

mdState=STARTED

mdNumDisabled=2

rdevStatus.3=DISK_DSBL

diskState.29=4

rdevStatus.29=DISK_NP_DSBL

Superblock has diskState.29=4 at byte offset 3852.

What I've tried:

• New SAS cables

• New HBA

• Editing disk.cfg to remove slot 29 entries (reverts on boot)

• Writing remove 29 to /proc/mdcmd — returns "Invalid argument" whether array is started or stopped

• Patching superblock byte offset 3852 from 0x04 to 0x00 — cleared all disk assignments unexpectedly, restored from backup

• Maintenance mode — /proc/mdcmd still rejects writes

• Unraid updated from 7.2.3 to 7.3.1 during troubleshooting — no change

Questions:

1. Is there a supported way to clear a ghost disabled Parity 2 slot from the superblock?

2. Is there a tool or procedure to force-clear slot 29 and drop mdNumDisabled to 1?

3. Why does /proc/mdcmd reject all writes even with the array stopped?

Data is intact and array is running degraded. No urgency but need a path forward.

Thanks!

12 hours ago, pdoroba said:

However there is a ghost Parity 2 slot (slot 29 internally) that is permanently stuck as DISK_NP_DSBL.

This is normal if there's no parity2

Please post the diagnostics.

Any idea how to fix this then? Disk 3 is showing as disabled. When i hover over the red X a pop up message states "Device is Disabled, Contents Emulated." I can't re-enable the disk and the SMART test returns no errors. Thanks!

11 hours ago, JorgeB said:

Please post the diagnostics.

As requested. Thanks!

seshat-diagnostics-20260614-1722.zip

How are you trying to re-enable the disk, are you doing this?

https://docs.unraid.net/unraid-os/using-unraid-to/manage-storage/array/replacing-disks-in-array/#re-enabling-a-disabled-disk-rebuilding-onto-itself

It took over 24 hours to run the extended SMART test. It completed without errors. I'll report back as I make progress. Thanks!

9 hours ago, pdoroba said:

It took over 24 hours to run the extended SMART test. It completed without errors. I'll report back as I make progress. Thanks!

That seems a reasonable time. I normally expect it to take something between 1 and 1.5 hours per TB (these operations on modern large disks take a long time😃). Good indication of disk health that it completed without errors.