A disk with "warning" message is missing in RAID5

mbinax · Jun 15th 2025

Hello,

about 4 years ago I set up the NAS with 6TB disks, which I configured in RAID5.

Since a few days I've been getting a warning message from the daily checks done by OMV, so I investigated and noticed that RAID 5 is on 5 disks (instead of all 6 installed ones); also, the missing disk has a "Warning" with "Bad sectors".

I guess I need to replace the disk, but what would be the correct procedure?

Could you point me to a guide?

Below you can see - from OMV GUI - the RAID configuration (labeled as "degraded."

Here you can see the detail of the missing disk, namely "sdb":

Finally, here is some data taken from CLI to help understand the overall situation:

Code

root@diynas-omv:/srv/dev-disk-by-label-RAID5/# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid0] [raid1] [raid10] 
md0 : active raid5 sdc[4] sdd[0] sdf[1] sde[5] sda[2]
      29301969920 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/5] [UUU_UU]
      bitmap: 40/44 pages [160KB], 65536KB chunk
unused devices: <none>

Code

root@diynas-omv:/srv/dev-disk-by-label-RAID5/# blkid
/dev/sdf: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="540cd822-1281-aead-7f6f-ca4f0842dc80" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"
/dev/nvme0n1p5: UUID="21dbc86c-cfc1-4b4a-a9ed-566388d70285" TYPE="swap" PARTUUID="5b2a273a-05"
/dev/nvme0n1p1: UUID="975fe369-9535-4459-80f8-f86795bdcb26" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="5b2a273a-01"
/dev/sdd: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="9e5d7091-039a-77b5-77b8-c3450cc7cac8" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"
/dev/sdb: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="f6d205c8-bc1a-5cd1-6a8a-7458a4b0c817" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"
/dev/md0: LABEL="RAID5" UUID="b143f942-1f22-42e0-b92d-4e4c557ff36c" BLOCK_SIZE="4096" TYPE="ext4"
/dev/sde: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="f5ddc7d4-d721-6796-e75e-733251246271" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"
/dev/sdc: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="1e112d20-45bd-32d0-9ebf-69bea2a73f9b" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"
/dev/sda: UUID="add77410-4af9-84b4-4a1b-f4c9a53296ae" UUID_SUB="93903863-bbf5-8435-c86f-c1dc338c5bb7" LABEL="DIYNAS-OMV:RAID5" TYPE="linux_raid_member"

Code

root@diynas-omv:/srv/dev-disk-by-label-RAID5/# fdisk -l | grep "Disk "
Disk /dev/nvme0n1: 232.89 GiB, 250059350016 bytes, 488397168 sectors
Disk model: Samsung SSD 970 EVO Plus 250GB          
Disk identifier: 0x5b2a273a
Disk /dev/sdc: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0095    
Disk /dev/sdf: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0095    
Disk /dev/sdd: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0095    
Disk /dev/sda: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0115-1YZ
Disk /dev/sde: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0115-1YZ
Disk /dev/sdb: 5.46 TiB, 6001175126016 bytes, 11721045168 sectors
Disk model: ST6000NM0115-1YZ
Disk /dev/md0: 27.29 TiB, 30005217198080 bytes, 58603939840 sectors

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Code

root@diynas-omv:/srv/dev-disk-by-label-RAID5/# cat /etc/mdadm/mdadm.conf
# This file is auto-generated by openmediavault (https://www.openmediavault.org)
# WARNING: Do not edit this file, your changes will get lost.


# mdadm.conf
#
# Please refer to mdadm.conf(5) for information about this file.
#


# by default, scan all partitions (/proc/partitions) for MD superblocks.
# alternatively, specify devices to scan, using wildcards if desired.
# Note, if no DEVICE line is present, then "DEVICE partitions" is assumed.
# To avoid the auto-assembly of RAID devices a pattern that CAN'T match is
# used if no RAID devices are configured.
DEVICE partitions


# auto-create devices with Debian standard permissions
CREATE owner=root group=disk mode=0660 auto=yes


# automatically tag new arrays as belonging to the local system
HOMEHOST <system>
# instruct the monitoring daemon where to send mail alerts
MAILADDR my-mail@my-domain.com
MAILFROM root


# definitions of existing MD arrays
ARRAY /dev/md0 metadata=1.2 name=DIYNAS-OMV:RAID5 UUID=add77410:4af984b4:4a1bf4c9:a53296ae

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Code

root@diynas-omv:/srv/dev-disk-by-label-RAID5/# mdadm --detail --scan --verbose
ARRAY /dev/md0 level=raid5 num-devices=6 metadata=1.2 name=DIYNAS-OMV:RAID5 UUID=add77410:4af984b4:4a1bf4c9:a53296ae
   devices=/dev/sda,/dev/sdc,/dev/sdd,/dev/sde,/dev/sdf

Thank you very much!

geaves · Jun 16th 2025

You can double check the drive removal by running mdadm --detail /dev/md0 from the cli

If you see 'removed' next to /dev/sdb then mdadm has remove the disk from the array, all you need to do is to replace the drive;

Shut down and remove the failed drive

Install a new drive -> start up

Storage Disks -> select the drive and do a quick/short wipe, this will prepare the drive for OMV to use

Raid Management/Md - Plugin there should be an option 'recover', click on that and your new drive should be displayed, select it and click OK the drive will then be added to the array

mbinax · Jun 26th 2025

Quote from geaves

You can double check the drive removal by running mdadm --detail /dev/md0 from the cli

If you see 'removed' next to /dev/sdb then mdadm has remove the disk from the array, all you need to do is to replace the drive;

Shut down and remove the failed drive
Install a new drive -> start up
Storage Disks -> select the drive and do a quick/short wipe, this will prepare the drive for OMV to use
Raid Management/Md - Plugin there should be an option 'recover', click on that and your new drive should be displayed, select it and click OK the drive will then be added to the array

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Confirmed, the drive is already removed, as you can see below.

Since this situation occurs, my NAS it stops and turns itself off.

When turned on (manually), I'm receiving mails like this one:

Code

This is an automatically generated mail message from mdadm

running on diynas-omv


A DegradedArray event had been detected on md device /dev/md0.


Faithfully yours, etc.


P.S. The /proc/mdstat file currently contains the following:


Personalities : [raid6] [raid5] [raid4] [raid0] [raid1] [raid10] 

md0 : active raid5 sdd[5] sda[2] sdc[4] sdf[1] sde[0]

     29301969920 blocks super 1.2 level 5, 512k chunk, algorithm 2 [6/5] [UUU_UU]

     bitmap: 44/44 pages [176KB], 65536KB chunk


unused devices: <none>

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I suppose this situation depends on the harddrive damaged, am I right?

Then... before proceeding to remove it, I'm just asking to myself how can I recognize the right drive to remove! Any idea also here?

geaves · Jun 26th 2025

Quote from mbinax

Since this situation occurs, my NAS it stops and turns itself off.

it shouldn't, so there could be another issue, i.e. hardware, intermittent power

Quote from mbinax

When turned on (manually), I'm receiving mails like this one:

That's normal if you have notifications enabled

Quote from mbinax

I suppose this situation depends on the harddrive damaged, am I right?

Not necessarily based upon your first quote about your machine stopping, mdadm could see that as a consistent fault and remove the drive

One option would be to run a SMART test on that drive, you should also check out this section in the user guide

Quote from mbinax

Then... before proceeding to remove it, I'm just asking to myself how can I recognize the right drive to remove!

Using OMV make a note of each drives serial number -> Storage -> Disks

mbinax · Jun 29th 2025

Thank you.

I've set SMART tasks to monitor my drives:

short self-test > weekly
long self- test > monthly

However, I am a bit concerned because now the drive that is reported "corrupted" is /dev/sda, whereas until a few days ago it was /dev/sdb.

I'm afraid both will have to be changed....

Currently, my RAID is made with 6TB drives (3x Seagate "ST6000NM0115-1YZ110", 3x Seagate "ST6000NM0095"): considering the cost of HDDs, should I gradually replace them with more modern and larger but (hopefully) less expensive HDDs?

Rd65 · Jun 29th 2025

It's not uncommon for multiple disks to fail one after the other in a RAID. They were usually purchased at the same time from the same batch and are subjected to the same load in the RAID. So why shouldn't they fail sooner? With six drives, you usually use a spare drive. And you usually have at least one spare disk in stock. RAID 5 doesn't mean it will last forever. It mean, it is easy to maintain without downtime - if you care right.
And by the way, 54° are much too warm for a Harddisk and constantly maybe a reason for dying drives.

geaves · Jun 30th 2025

Quote from mbinax

However, I am a bit concerned because now the drive that is reported "corrupted" is /dev/sda, whereas until a few days ago it was /dev/sdb

If you are restarting your server (shutdown/reboot) then the drive references can change, this makes it more difficult to identify which drive is the problem, unless you have written information of each drive in your system

Quote from mbinax

considering the cost of HDDs, should I gradually replace them with more modern and larger but (hopefully) less expensive HDDs

Personally I would not run Raid5 with more than 4 drives I would use Raid6, this is a personal choice

You'll only need larger drives if you require more space and replacing then 'gradually' would mean the array cannot 'grow' to it's new size until the last drive has been replaced.

Yes, replace them with conventional drives

When you buy new drives make sure they are CMR not SMR, whilst SMR are cheaper per data storage they can be an issue when using Raid

mbinax · Jun 30th 2025

Quote

Yes, replace them with conventional drives

What do you mean for "conventional"?

Maybe "CMR" is conventional?

geaves · Jul 1st 2025

Quote from mbinax

What do you mean for "conventional

WD Red's, Seagate Iron Wolf

I have searched the drive references you have posted and they come as Enterprise drives, these are more expensive

A disk with "warning" message is missing in RAID5

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