ReadyNAS NV+ v2 - hdd intermittenly drops connection

Hi Spielhaug 

The situation is not good. I can see you have been using two different size disks (likely 2x2TB 2x3TB?). This in itself is fine but it creates two raids on top of each other.

In the below raid output we would expect to see md0 (OS raid), md1 (swap raid), md2 (data raid 1) and md3 (data raid 2). md2 is completely missing and all the other raids are degraded.

Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4]
md3 : active raid5 sdd4[0]
976750784 blocks super 1.2 level 5, 64k chunk, algorithm 2 [2/1] [U_]

md1 : active raid1 sda2[4]
524276 blocks super 1.2 [4/1] [U___]

md0 : active raid1 sda1[4]
4193268 blocks super 1.2 [3/1] [U__]

unused devices: <none>

The data volume cannot mount as a result of the missing md2 and you only see the OS volume information (information for volume "C", the data volume, is missing). At this point, access to the data is lost. You will be able to see some shares appear as folders but the content is not there. Neither can you write to the volume.

Filesystem Size Used Avail Use% Mounted on
/dev/md0 4.0G 763M 3.1G 20% /
tmpfs 16K 0 16K 0% /USB

This situation most certainly occurred because of the disks dropping in and out of the raids causing double or even triple disk failures in the array. Your disks look fine from a healthcheck point-of-view. I can see you inserted a newer one though but that won't do much as the data raids are already in trouble. I don't see the disks in the past actually being bad. One of the disks had some errors on it, but only 2 ATA errors - you replaced that one.

The 3 others appear fine yet still, we see disks dropping in and out.

3!!Thu Feb 21 17:28:58 CET 2019!!root!!Disk removal detected. [Disk 1]
3!!Thu Feb 21 17:35:36 CET 2019!!root!!Disk removal detected. [Disk 2]
3!!Fri Feb 22 06:47:39 CET 2019!!root!!Disk removal detected. [Disk 2]
3!!Fri Feb 22 06:47:39 CET 2019!!root!!Disk removal detected. [Disk 3]

The above happens over and over and this will surely have been messing up your data raids and in turn your volume.
I suspect that perhaps the back-plane might be bad given that you didn't perform these actions.

Do you have a backup of the data? I think data recovery is possible here, granted that we have at least 3 healthy disks that seems to be have been part of the raid before it went south. However, it would be wise to let NETGEAR do that part if you really need the data back. It will cost a data recovery contract which is a couple hundred bucks or something along those lines.

If you have a backup or don't need the data then a factory default would probably be the best option. However, I would be concerned myself to use the NAS as this issue here is possibly chassis related. I would advise that you test each disk with a tool from manufacturer to ensure the disks are fully OK. At that point you can start suspecting the chassis might be faulty.

Cheers