HDD failure: Why is my NSA325v2 beeping and inaccessible?

We move across the ocean and, as assumed, one HDD of my NSA did not survive. When I start the NSA now, drive 1 shows a red LED sign, the green activity LED is blinking and the system is beeping continuously. Even after waiting 8h, no change in the condition, need to switch the NSA off at night, that our little one can sleep.

Worst is, that I cannot access the browser backend GUI, when the system is in that state. Only, when I take off HDD 1 (and I leave the healthy one in) I have access to the settings GUI. However, I like to try to format the broken disk or anything, but this is not possible for now. 

Is there any solution so that I can access the NSA when the broken one is inserted to format it?
Also, I cannot find this behaviour in the troubleshooting of the documents. What does the continuous beeping in combination with a busy NSA mean?


#NAS_Jul_2019