Problem with login when one node is offline

[suriv]

Hi,

Hi, I faced strange problem last week. I have 2 nodes cluster for testing. Due to RAM upgrade I had to power off one node. When one node was powered off I tried to login to web panel but it failed. I was sure that the password was correct. When I checked the logs I found that problem is with quorum. To be able to log in I had to call "pvecm expected 1" via SSH and then I was able to log in. The question is, why is quorum required for login and if there is no quorum shouldn't the user be allowed to login without it?

 

[sterzy]

Hi,

Well a user logging in requires a quorum because they might change configurations that affect the whole cluster. A node cannot distinguish between the cluster being down or unreachable, so if it allowed a user to log in and then another user logs into the rest of the cluster a split brain condition might arise. This can result in instability and data corruption.

A two node set up is not recommended by itself and you should set up a QDevice [1] to avoid such issues.

[1]: https://pve.proxmox.com/pve-docs/pve-admin-guide.html#_corosync_external_vote_support