NAS542 Raid 1 failure so Datas are on the Disk but didnt shown in File direktory

Darkmasterwulf

Hi,

two days ago my NAS542 started behaving very strangely. Suddenly it beeped and the first two hard drives were briefly gone during a write process. After a short time the NAS restarted and started restoring the Raid 1 partition. This took almost 32 hours with just under 6TB. Afterwards I thought ok, everything was back but I was far from it. The raid seems empty. However, I took out the hard drives and tried to read them on my PC. Using a recovery tool I can see that the two disks are full and still contain data. However, these will live on a file system and can only be restored even without the correct name. How can this be since both hard drives have no errors? I'm trying to restore the data now, but I would like an explanation.

Mijzelf

That restart is strange. When a disk of a raid1 array fails, the NAS is supposed to simply warn you by beeping and by email, if you configured that, but it should continue normally. A spontaneous reboot is bad.

The most straight forward reason for loosing your volume content is a filesystem error. That can be caused by a power failure, or some major fault which causes the NAS to reboot without proper shutdown. The same cause can initiate a raid resync. The arrays both have a header containing a last update timestamp. Those stamps are supposed to be identical. If they are not, the most recent one is supposed to be the 'current' one, and the other can be synced. Conceptually those stamps are written simultaneously, but in real world they are not. If you pull the power at the wrong moment, one disk is updated, and the other is not.