Slow SSH on Proxmox

I just switched my Hetzner Dedicated Server (AX41-NVMe) to ZFS (RAIDZ-1) and now SSH is super slow for some unknown reason.

  • I have correctly configured ZFS (2GB RAM)
  • I have setup Fail2Ban (thought maybe it was getting hammered)
  • Overall system performance seems fine. Plenty of free Processor, RAM and Disk according to the amazing HetrixTools :slight_smile:
  • When I access the Shell from the WebGUI, everything seems normal.
  • rebooted a couple of times now

What else can I do / check?

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Try logging in through another machine. If it feels sluggish then there is something wrong with the network. But its just my assumption so run MTR. And try to boot the machine in rescue mode and log in via ssh so that you can be sure its not the network.

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I assume your UseDNS is set to no?

That’s usually only delays logging in after that it doesn’t have much affect.

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Yeah, true.

@aaronstuder What’s the ping like between the server and where you’re connecting from?

Around 140ms. It was fine before this.

When you say slow, do you mean when it’s connecting or when you’re logged on and your node feels slow/sluggish?

Drop into sh, exec sh - speedier? Is terminal compression enabled in your client? It’s enabled by default in /etc/ssh/sshd_config, but client needs to implement as well. Which part is slow? Acknowledgement on the keystroke from the terminal or running a command in terminal?

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UPDATE: This morning everything seems fine? Maybe connections issues from the US to Finland?

Very possible, always could setup smokeping and monitor it to various endpoints and monitor it over a period of time.

On another note, if your dealing with ~100+ms connections all the time and you want a silky smooth SSH session, you could look into using/setting up mosh (

It’s also very handy for road warrior users as it handles dropped connections well (think of tweaked screen or tmux). Simple to setup and no real difference once its setup then a regular ssh session (ssh runs on top).

Won’t bore everyone here why its smoother/faster, but have a little research/read about it, if the SSH delay gets annoying.