I tried to put the failing drive back. The NAS started without any weird noise, but the storage pool was still degraded and drive 2 still undetected. I may have done something wrong. But your advice will be precious. Have a great day!
I have restarted the NAS from the user menu and then the drive was detected. But I had torepairthe RAID, as the drive was considered new to the storage manager. The disks are two identical Crucial MX500 SSD disks, and I'm using the latest DSM 7.2. ...
were in, the data was accessible despite all the warnings. So my solution was to simply copy all of the data to the new NAS via SMB and delete the broken storage pool. Probably the Synology support would have found a more elegant solution given more time, but this seemed safer and ...