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I have a 5 year old PR4100 with 4 x 2TB WD red's. It was always configured in the default Raid1 setting. A week ago, my PR4100 showed a red led on the first drive. My files were still accessible and everything was working fine. When running a quick drive test, the dashboard showed that drive 3 was failing. This seemed a bit odd to me so I restarted the NAS.

After the restart, all drives show a red led on the system. My files and shares aren't accessible anymore and it seems as if the drives aren't mounted. The dashboard shows that I need to configure a raid volume again. I obviously don't want to do this as this would wipe the drives. I normally had raid rebuild set on automatic but this function is now missing from the dashboard.

Running a full test again, the system says drive 3 should be replaced. Today I received a new, identical 2TB WD red HDD and replaced drive 3. I somehow hoped that this would magically start rebuilding the raid but the NAS just does...nothing. Doing another drive test, all drives appear healthy although all 4 drives have red led's on the system.

I can still log in to the dashboard, have full acces to SSH but can't acces files in any way. I think it has something to do with the raid configuration or profile missing.

I haven't read or write any files to the HDD's since the errors so I'm hoping all my very personal files on the nas aren't damaged or gone in any way. But I have no idea how to go forward. Manually start rebuilding the raid from SSH? Retrieve or change the missing raid profile? Any help is very much appreciated!

root@MyCloudPR4100 ~ # mdadm --detail /dev/md0
/dev/md0:
           Version : 1.2
     Creation Time : Sat Feb 11 11:13:50 2023
        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 : Sat Feb 11 11:13:53 2023
             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 : c93335dc:dd795ea9:4612ae75:b4b3e02d
            Events : 5

    Number   Major   Minor   RaidDevice State
       0       8        1        0      active sync   /dev/sda1
       1       8       17        1      active sync   /dev/sdb1
       2       8       49        2      active sync   /dev/sdd1
       -       0        0        3      removed

root@MyCloudPR4100 ~ # cat /proc/mdstat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] 
md0 : active raid1 sdd1[2] sdb1[1] sda1[0]
      2094080 blocks super 1.2 [4/3] [UUU_]
      bitmap: 0/1 pages [0KB], 65536KB chunk

Full kernel info: https://pastebin.com/Du2HJ7kZ

output of mdadm --examine /dev/sd* in this pastebin: https://pastebin.com/u3BA6FuR

WIWIWWIISpitFire
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  • `mdadm --examine /dev/sd*`? (including the missing drive, if still operational) md0 seems to be used for swap, that's not interesting, you're supposed to look into this `md/raid:md1: not enough operational devices (2/4 failed)` – frostschutz Feb 11 '23 at 20:13
  • Thanks @frostschutz, you obviously know your stuff, I don't. I added the output of `mdadm --examine /dev/sd*` in this pastebin: https://pastebin.com/u3BA6FuR What does this show? Multiple profiles? Looking into "not enough operational devices" doesn't necessary bring me to new info. – WIWIWWIISpitFire Feb 11 '23 at 20:36
  • OK, something very strange happened to /dev/sdc (wrongly used without partition table). Did you do that manually? You might be able to recover its partitioning same as on the other drives and hopefully find intact metadata as /dev/sdc2. Without it, you have sd[abd]2 so one drive missing entirely. However sda2 considers itself spare. Unless you can recover sdc2 partition to save the day, only way to proceed [would be to re-create the array](https://unix.stackexchange.com/a/131927/30851). And even that would only work if sda2 had good data, despite its spare status. – frostschutz Feb 11 '23 at 23:11
  • Okay that sounds like something I would like to try. I found a bunch of meta data before (don’t reminder the terminal command). Can you help me with this @frostschutz? I have no idea how to do something you said here above – WIWIWWIISpitFire Feb 12 '23 at 06:39

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