PR4100 Raid configuration disappeared

Hi everyone,
I have been using the nas for over 6 months. Never had any issues. Today I am seeing 4 solid red lights underneath the disk arrays, the system is down. I logged in to the dashboard and it says 0mb available. I checked the disk the disk status are all healthy. However the raid configuration seems to have just disappeared. On the storage->raid profile-> Raid health it says no configured volumes , setup a Raid mode to configure new Raid volumes on this device.
I tried the following options - (1) reboot, (2)shutdown and removed and inserted the disks and powered up,(3) shutdown and removed the disk and powered up and shutdown again and then inserted the disks and powered up. All the steps the lights turn blue and flickered until it starts and then goes back to solid red.
I ran the quick system diagnostics it didn’t pick up anything. I am now running the full test and it’s running for a while now…

Is there any way to bring my system back to how it was before ? Or the only option is to reconfigure raid and lose all the data ?

Has anyone came across this issue ? Any suggestions would be of great help. Thanks


Hello chelvamst,

Unfortunately, the only resolution to this is to set up the RAID again. I am afraid that is going to erase everything from the drive.

My PR4100 running Raid5 with 4 6TB drives just did the same thing. It was about 95% full containing acronis system backups. I was attempting to log onto it to cull the older backups when it changed from full capacity to zero capacity and no raid configured. It apparently lost the raid configuration.
In my past experience, I’ve been able to recover from a raid configuration issues on other systems by putting similar blank drives into the unit, configuring it identically to what it had been and then swapping the drives out for the originals. That did not work for this unit. My guess is raid information stored on the drives somehow got corrupted.

Any thoughts on how I might recover the data would be hugely appreciated. Hoping the only answer is not really all data is lost.

Hi randraka ,

Maybe you should try contacting WD’s Technical Support about this.

To Contact WD for Technical Support

For missing RAID configurations, feel free to SSH into your box and provide the output for each of following commands:

System info

uname -a

RAID status

cat /proc/mdstat
mdadm --detail /dev/md0
mdadm --detail /dev/md1

Disk info

gdisk -l /dev/mmcblk0
gdisk -l /dev/sda    [same for /dev/sdb, /dev/sdc, /dev/sdd]

Kernel info


This last one is quite fat, please post it to pastebin and just provide the link here.
I may be able to help you but I need all this info.

Note: SSH access is at your own responsibility and risk. These commands just print information, but some of these tools can also be used to wipe disks, resulting in data loss and even bricking your NAS. It is advised to create a USB rescue disk.

Hi Tfl - I have the same problem, drive 1 was showing red for one year, other 3 raid 5 were fine. Finally I changed drive 1 to JBOD 2 days ago and now all the others are red, no volume.

root@MyCloudPR4100 dev # mdadm --D /dev/md0
mdadm: unrecognized option ‘–D’
Usage: mdadm --help
for help
root@MyCloudPR4100 dev # mdadm -D /dev/md0
Version : 1.2
Creation Time : Sun Nov 22 17:20:50 2020
Raid Level : raid1
Array Size : 2094080 (2045.00 MiB 2144.34 MB)
Used Dev Size : 2094080 (2045.00 MiB 2144.34 MB)
Raid Devices : 4
Total Devices : 3
Persistence : Superblock is persistent

 Intent Bitmap : Internal

   Update Time : Sun Nov 22 17:32:44 2020
         State : clean, degraded
Active Devices : 3

Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Consistency Policy : bitmap

          Name : MyCloudPR4100:0  (local to host MyCloudPR4100)
          UUID : 8996083b:975be7a1:673eb395:843c62bc
        Events : 7

Number   Major   Minor   RaidDevice State
   0       8        1        0      active sync   /dev/sda1
   1       8       17        1      active sync   /dev/sdb1
   2       8       33        2      active sync   /dev/sdc1
   -       0        0        3      removed

root@MyCloudPR4100 dev #

can you help?](

Hi Tfl,

Face issue in my raid… Please help suddenly it got disappear.

I extract detail using command can you please check on below: