+----
+
+The new link will be enabled as soon as you follow the last steps to
+xref:pvecm_edit_corosync_conf[edit the corosync.conf file]. A restart should not
+be necessary. You can check that corosync loaded the new link using:
+
+----
+journalctl -b -u corosync
+----
+
+It might be a good idea to test the new link by temporarily disconnecting the
+old link on one node and making sure that its status remains online while
+disconnected:
+
+----
+pvecm status
+----
+
+If you see a healthy cluster state, it means that your new link is being used.
+
+
+Corosync External Vote Support
+------------------------------
+
+This section describes a way to deploy an external voter in a {pve} cluster.
+When configured, the cluster can sustain more node failures without
+violating safety properties of the cluster communication.
+
+For this to work there are two services involved:
+
+* a so called qdevice daemon which runs on each {pve} node
+
+* an external vote daemon which runs on an independent server.
+
+As a result you can achieve higher availability even in smaller setups (for
+example 2+1 nodes).
+
+QDevice Technical Overview
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The Corosync Quroum Device (QDevice) is a daemon which runs on each cluster
+node. It provides a configured number of votes to the clusters quorum
+subsystem based on an external running third-party arbitrator's decision.
+Its primary use is to allow a cluster to sustain more node failures than
+standard quorum rules allow. This can be done safely as the external device
+can see all nodes and thus choose only one set of nodes to give its vote.
+This will only be done if said set of nodes can have quorum (again) when
+receiving the third-party vote.
+
+Currently only 'QDevice Net' is supported as a third-party arbitrator. It is
+a daemon which provides a vote to a cluster partition if it can reach the
+partition members over the network. It will give only votes to one partition
+of a cluster at any time.
+It's designed to support multiple clusters and is almost configuration and
+state free. New clusters are handled dynamically and no configuration file
+is needed on the host running a QDevice.
+
+The external host has the only requirement that it needs network access to the
+cluster and a corosync-qnetd package available. We provide such a package
+for Debian based hosts, other Linux distributions should also have a package
+available through their respective package manager.
+
+NOTE: In contrast to corosync itself, a QDevice connects to the cluster over
+TCP/IP. The daemon may even run outside of the clusters LAN and can have longer
+latencies than 2 ms.
+
+Supported Setups
+~~~~~~~~~~~~~~~~
+
+We support QDevices for clusters with an even number of nodes and recommend
+it for 2 node clusters, if they should provide higher availability.
+For clusters with an odd node count we discourage the use of QDevices
+currently. The reason for this, is the difference of the votes the QDevice
+provides for each cluster type. Even numbered clusters get single additional
+vote, with this we can only increase availability, i.e. if the QDevice
+itself fails we are in the same situation as with no QDevice at all.
+
+Now, with an odd numbered cluster size the QDevice provides '(N-1)' votes --
+where 'N' corresponds to the cluster node count. This difference makes
+sense, if we had only one additional vote the cluster can get into a split
+brain situation.
+This algorithm would allow that all nodes but one (and naturally the
+QDevice itself) could fail.
+There are two drawbacks with this:
+
+* If the QNet daemon itself fails, no other node may fail or the cluster
+ immediately loses quorum. For example, in a cluster with 15 nodes 7
+ could fail before the cluster becomes inquorate. But, if a QDevice is
+ configured here and said QDevice fails itself **no single node** of
+ the 15 may fail. The QDevice acts almost as a single point of failure in
+ this case.
+
+* The fact that all but one node plus QDevice may fail sound promising at
+ first, but this may result in a mass recovery of HA services that would
+ overload the single node left. Also ceph server will stop to provide
+ services after only '((N-1)/2)' nodes are online.
+
+If you understand the drawbacks and implications you can decide yourself if
+you should use this technology in an odd numbered cluster setup.
+
+QDevice-Net Setup
+~~~~~~~~~~~~~~~~~
+
+We recommend to run any daemon which provides votes to corosync-qdevice as an
+unprivileged user. {pve} and Debian provides a package which is already
+configured to do so.
+The traffic between the daemon and the cluster must be encrypted to ensure a
+safe and secure QDevice integration in {pve}.
+
+First install the 'corosync-qnetd' package on your external server and
+the 'corosync-qdevice' package on all cluster nodes.