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[Help] Hard Drive reporting unmounted and storage pool degraded?
Posted: 06 Oct 2026, 19:55
by t4rex
I've got 4 8TB WD Blue hard drives in my F4-212. I've had TOS saying drive 2 is unmounted but everything seems to be working ok? I did a restart yesterday and the drive no longer said unmounted.
But this morning I got a notification saying, the raid in storage pool 0 has been degraded but it was reporting all 4 disks were normal and in good condition. Only after a restart did it say disk 2 was unmounted?
thanks!
Re: [Help] Hard Drive reporting unmounted and storage pool degraded?
Posted: 06 Oct 2026, 21:08
by MikeZhang
Your symptoms — recovery after reboot, recurrence after some time, and disk 2 showing "unmounted" again after another reboot — point to an intermittent connection or response issue with HDD2. The drive may not be completely dead, but under load fluctuations, temperature changes, or slight vibration, it can briefly drop out of the array and trigger a degraded alert. After a reboot it is recognized again and the array rebuilds, so it looks normal — but the underlying problem remains.
Recommended troubleshooting steps:
1. Physical check (first priority)
Power down, remove HDD2, and inspect the connector contacts for oxidation or contamination.
Reinsert it and make sure the tray is fully seated and latched.
Swap HDD2 and HDD3 between bays to determine whether the issue follows the drive or the bay:
If it follows the drive → the drive itself is faulty.
If it stays in the original bay → the bay or backplane connection is faulty.
2. Identify the failing drive (via SSH)
If the issue recurs while TOS still shows "Good", log in via SSH to confirm:
Run cat /proc/mdstat and look for the drive marked (F) in the array output.
Then run smartctl -a /dev/sdX (replace with the actual device) and check:
Reallocated_Sector_Ct
Current_Pending_Sector
Offline_Uncorrectable
If any of these show a non-zero value, the drive has physical damage. Back up your data and replace it as soon as possible.
Re: [Help] Hard Drive reporting unmounted and storage pool degraded?
Posted: 06 Oct 2026, 23:52
by t4rex
It looks like the drive is failing?
Code: Select all
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x002f 001 001 051 Pre-fail Always FAILING_NOW 19457
3 Spin_Up_Time 0x0027 235 187 021 Pre-fail Always - 5241
4 Start_Stop_Count 0x0032 100 100 000 Old_age Always - 357
5 Reallocated_Sector_Ct 0x0033 198 198 140 Pre-fail Always - 94
7 Seek_Error_Rate 0x002e 200 200 000 Old_age Always - 0
9 Power_On_Hours 0x0032 084 084 000 Old_age Always - 12028
10 Spin_Retry_Count 0x0032 100 100 000 Old_age Always - 0
11 Calibration_Retry_Count 0x0032 100 253 000 Old_age Always - 0
12 Power_Cycle_Count 0x0032 100 100 000 Old_age Always - 20
192 Power-Off_Retract_Count 0x0032 199 199 000 Old_age Always - 1491
193 Load_Cycle_Count 0x0032 171 171 000 Old_age Always - 87823
194 Temperature_Celsius 0x0022 120 114 000 Old_age Always - 32
196 Reallocated_Event_Count 0x0032 106 106 000 Old_age Always - 94
197 Current_Pending_Sector 0x0032 200 200 000 Old_age Always - 900
198 Offline_Uncorrectable 0x0030 100 253 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x0032 200 200 000 Old_age Always - 0
200 Multi_Zone_Error_Rate 0x0008 100 253 000 Old_age Offline - 0
time to replace I guess, thanks!
Re: [Help] Hard Drive reporting unmounted and storage pool degraded?
Posted: 07 Oct 2026, 01:50
by EriChan
t4rex wrote: ↑06 Oct 2026, 23:52
Yes, the hard drive is failing and needs to be replaced immediately.
The SMART attributes confirm hardware failure:
- ID 1 (Raw_Read_Error_Rate): The value has dropped below the threshold and is reporting FAILING_NOW.
- ID 5 (Reallocated_Sector_Ct): Has 94 reallocated bad sectors.
- ID 197 (Current_Pending_Sector): Has 900 pending sectors waiting to be remapped.
Due to excessive read errors and I/O timeouts, the system dropped/unmounted the disk to protect data integrity, causing the storage pool to enter a degraded state.
Recommended Steps:
1. Back up critical data: While the degraded pool remains accessible, ensure your important data is backed up first.
2. Prepare a replacement drive: Go to Storage Manager > Storage Pool > More > Repair Array, check the required disk type and capacity specified in the prompt, and prepare an appropriate replacement disk.
3. Power off and replace the disk: Short press the power button to shut down the TNAS. Once the power LED turns completely off, pull out the faulty drive and insert the replacement disk meeting the requirements.
4. Power on and rebuild the array: Short press the power button to turn on the TNAS. Go to Storage Manager > Storage Pool > More > Repair Array > Select Drive > Confirm Settings, and wait until the array synchronization completes.
Hope this helps!