HA affinity rules
in Proxmox VE

Control over cluster placement

In an HA cluster the manager decides which node to restart a VM on after a failure. Without hints it may place two VMs that should be separated side by side — or split apart those that must stay close.

HA rules give you that control declaratively. The config lives in /etc/pve/ha/rules.cfg under /etc/pve, so it is distributed to every node automatically — the whole cluster shares one consistent rule set. You can also set them in the UI: Datacenter → HA → Rules.

Affinity, anti-affinity and node affinity

• Node affinity — pin a resource to chosen nodes. Replaces the old HA groups and is feature-compatible with them.
• Resource affinity (positive) — keep selected VMs on the same node (e.g. an app close to its database).
• Resource anti-affinity (negative) — spread VMs across different nodes, so a single host failure doesn't take down a whole redundant service.

Hard and soft constraints

Node affinity rules are non-strict by default: if none of the listed nodes is available, the VM still starts elsewhere — availability wins. When the dependency is hard (e.g. a license tied to specific hardware, or local storage), use a strict rule — then the manager limits placement, recovery and migration to the rule's nodes only.

Return behaviour is governed by the failback flag (on by default) — once the preferred node is back, the VM returns to it. It's the successor of the old nofailback from HA groups, moved onto the HA resource.

From HA groups to rules

• Automatic migration — on upgrade to 9.x, old HA groups are converted to node affinity rules and the group assignment moves into the rule's "resources" field.
• Start with anti-affinity for redundant pairs — the biggest reliability gain for minimal effort.
• Strict only when needed — too many hard rules can block failover. The default soft mode is safer.