Nether lags dedicated servers

Can you provide a copy of an affected world?

I personally cannot as I am not the owner of these servers, I admin one but the rest of the information has come from other users using different hosts and it's the same results, even loaded up a brand new world and going in causes this 

Would BDS-19101 describe your issue?

The CPU only got as high as 17% and immediately dropped down to around 3% after loading the nether.

When entering the nether it lags the entire server including the overworld dimension and continues to lag until the user(s) leave the nether dimension, after they leave the lag is gone and everything goes back to normal, have also noticed when moving around in the nether chunks take awhile to load they're just giant areas of emptiness until they do load 

Our server is suffering from the same issue, as well as BDS-19101.  Going through a portal can takes minutes to happen and the CPU usage spikes to 100% throughout that time.  However once the nether eventually loads for the player CPU usage drops back to standard levels, however the world in all 3 dimensions is incredibly laggy.  eating can take 4-5 attempts, blocks break and place eratically, and so on6

Ian plant Would you be able to provide a copy of an affected world?

It was a brand new world. The server was very busy between 20-30 players online at a time. We found a fix which was drastically increasing the compression number on the server. It fixed both issues

@Ian plant could you share what you did that fixed your issue?

Can confirm this is still an issue in version 1.21.2.02

@Ian plant How 'drastic'?  I set mine to 50000 and was still seeing issues.  I guess I could max it out but was wondering how high you went.  Maybe there's a "sweet spot"

I can confirm this is still an issue as is BDS-19101

We are running a BDS server with 6 cores and it's maxing out or CPU on multiple cores when people go into the Nether.

I have the same isue like you with my server 1.21.3.01
I have 48 core 768gb ram but 100% cpu on all core when someone go in nether. with any cpu core (4,8 16 or all core) and options in config file

This is a duplicate of BDS-19101

 I have this issue on my BDS as well and made a ticket about it last year here: BDS-19244

Interestingly, my server's issue is a bit different than the ones described here and at BDS-19101

I have the long nether loading time, which is alleviated when turning the render distance down. Also have chunks that refuse to load for 30+ seconds, which is present even with lowest render distance. However, eating and flying are normal (not laggy as described in this ticket). And server CPU usage does not spike to 100% but goes up to around 60% for the duration of loading.

I'm having the same issue. Any time someone enters a nether portal the server lags for a few seconds-mins. Sometimes the loading screen to the nether takes 5 mins. A few times when someone has entered the nether they have crashed the server. I also noticed mobs are not despawning.  

Also experiencing this issue on the server I play on.