Proxmox 3.x IP hot/cold failover for static site

[Humbug]

Hi,
i'm looking for advice on a simple hot/cold IP failover setup for a static site (no database replication necessary). I have two Proxmox 3.x servers/hosts running and want to have two identical VMs on the hosts with their own hard disks - so no shared disks or data migration are involved. In case vm1 on host1 fails, i want vm2 on host2 to start and take over the IP of vm1.
Is this something Proxmox 3.x can do for me?

thanks,
Humbug

 

[Patrick Zippenfenig]

Hi,
i use keepalived to float a single IP between VMs. You can also add additional checks for your server or similar.

Regards,
Patrick

 

[Humbug]

Hi Patrick,
sounds interesting! Does your keepalive setup need a loadbalancer? Or do both hosts work independently?
Best,
Humbug

 

[Patrick Zippenfenig]

Both hosts work independently. You could use keepalived as a loadbalancer. Basic setup:
2x keepalived VMs which share a single and load-balance traffic to nodes

In my case I use 2x Nginx VMs as proxy load-balancer with 2x floating IP and DNS load balancing. If one host is down, the second host gets both IPs.

Works well with LXC

 

[Humbug]

Is your setup similar to the one described in this document?
https://www.cyberciti.biz/faq/rhel-centos-fedora-keepalived-lvs-cluster-configuration/

 

[Patrick Zippenfenig]

It is a good start. Keepalived offers 2 important features:
- Floating IP with VRRP for High Availability
- Load Balancing on layer 3 or 4

I use floating IP and Nginx for load-balancing and SSL and HTTP2 termination. I highly recommend using gratuitous ARP with keepalived. A switch reboot could lead to unexpected problems.

Under rare conditions keepalived could trigger periodic kernel messages "unregister_netdevice: waiting for lo to become free. Usage count = 1". It sometimes happens after I try to delete a container that used keepalived. Delete does not succeed until host restart. Could be related to https://github.com/moby/moby/issues/5618.