Acceptable server but very weak performance (docker installation)

Hello Jitsi Community,

I am a Jitsi-beginner with moderate experience with Linux and servers. Last week I rented a server to set up a Jitsi-Meeting-instance, because i checked it out and it looks very nice. I need it for my university department to communicate with colleagues.

My rented server is (@ STRATO.de):

CPU: Intel Xeon E-2126G (Coffee Lake, 6 x 3,3 GHz)

MEM: 32 GB DDR4 ECC RAM

HD: 2 x 480 GB SSD

NET: 1 GBit/s

OS: Ubuntu 18.04 LTS 64bit

I installed Jitsi via Docker Compose (https://github.com/jitsi/docker-jitsi-meet), open the right ports (443 and 80), enabled redirection to https and ordered the TLS-certificate at Let’s Encrypt.

Prinicpally everything works. When I meet one or too colleagues at a meeting the quality is super or quite good. But when we meet together for example 6 or more colleagues, the quality begin to be unacceptable. Video and voice often have discrepance and delay. They freeze sometimes for 2 seconds and more. Some participants fall out of the connection and have to reconnect.

Have you any ideas, what could be the problem? I think, that the server is “strong” enough for - I thought - 20 or 30 participants? Do you have any experiences or ideas?

Thank you very much!
Konrad