1---
2layout: "docs"
3page_title: "High Availability"
4sidebar_current: "docs-concepts-ha"
5description: |-
6  Vault can be highly available, allowing you to run multiple Vaults to protect against outages.
7---
8
9# High Availability Mode (HA)
10
11Vault supports multi-server mode for high availability. This mode protects
12against outages by running multiple Vault servers. High availability mode
13is automatically enabled when using a storage backend that supports it.
14
15You can tell if a backend supports high availability mode ("HA") by
16starting the server and seeing if "(HA available)" is outputted next to
17the backend information. If it is, then HA will begin happening automatically.
18
19To be highly available, Vault elects a leader and does request forwarding to
20the leader. Due to this architecture, HA does not enable increased scalability.
21In general, the bottleneck of Vault is the storage backend itself, not
22Vault core. For example: to increase scalability of Vault with Consul, you
23would scale Consul instead of Vault.
24
25In addition to using a backend that supports HA, you have to configure
26Vault with an _advertise address_. This is the address that Vault advertises
27to other Vault servers in the cluster for request forwarding. By default,
28Vault will use the first private IP address it finds, but you can override
29this to any address you want.
30
31## Backend Support
32
33Currently there are several backends that support high availability mode,
34including Consul, ZooKeeper and etcd. These may change over time, and the
35[configuration page](/docs/config/index.html) should be referenced.
36
37The Consul backend is the recommended HA backend, as it is used in production
38by HashiCorp and its customers with commercial support.
39
40If you're interested in implementing another backend or adding HA support
41to another backend, we'd love your contributions. Adding HA support
42requires implementing the `physical.HABackend` interface for the storage backend.
43