Why is server often off?

I invited 2 my friends and about 800 players who can join the server in Youtube videos.
So please if you make the server closed (i don't care with what reason) then your server is loosing about 50% players
Here is an useless map but looks cool (where do the players come from)
Second question: What is up with that 30 slots server?

We're experiencing huge hosting problems. Currently we are hosting on JiHost, the 30-slot host is on Volt-Host. JiHost crashes after every 17-24 hours. Volt-Host crashes every 5 minutes. Thats why we choose to stay on JiHost for now. Volt-Host has an crashrestarter, and JiHost not. But a crashrestarter won't help if the server crashes every 5 minutes. Im really doing my best to keep the server online, currently im discussing with both hosts. If they don't get a fix ill simply search for another host.

EDIT: Crashes on JiHost are fixed, not sure if its permanently.

Thanks for answer. I expected something like that.