Due to the very slow LAN transfer, I performed several checks and verifications (but this is another story). During the disk quick check, the power supply was interrupted. Since, I am not in position to get any access to this NAS (it has a dedicated IP number in the router). Even after 4 s or 40 s (power-off) reboot, the power led remains solid red. The NAS is no more visible on the LAN.
The leds of both HD are solid blue.
When switching the NAS on, the power led starts blue blinking, but at the end switch to solid red.
Do you have any idea how to fix this issue and how to get access to the monitoring ?
Thank you Cerberus for your quick reply.
Actually this was a stupid issue due to an incorrect plug of the ethernet cable into the switch - apologies for posting this. I should have checked before
However, several resets helped me to recover fast (acceptable) LAN data transfer.