[PATCH docs 2/2] ha-manager: add requirements for ha-managed vms and containers

[Daniel Kral <d.kral@proxmox.com>]

The HA Manager implicitly requires certain conditions that VMs and
containers need to fulfill to be handled correctly by the HA Manager.

Make the most important conditions explicit by writing them out in the
HA resources section and add a paragraph what role HA rules play here to
accomodate for HA resources, which do not meet all of these
requirements.

Signed-off-by: Daniel Kral <d.kral@proxmox.com>
---
 ha-manager.adoc | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/ha-manager.adoc b/ha-manager.adoc
index 6bf4e69..599622a 100644
--- a/ha-manager.adoc
+++ b/ha-manager.adoc
@@ -135,6 +135,26 @@ consists of the resource type and a type-specific ID, which is the VMID
 for VMs and containers. For example, for the VM with VMID `100`, the
 service ID is `vm:100`.
 
+In general, HA resources need to be setup in such a way, so that they are
+able to run on any cluster node. Therefore, a VM or container should meet
+the following requirements before it is added as an HA resource:
+
+* use options, which are compatible on all nodes
+
+* only use shared storage, which are available on all nodes
+
+* only use network interfaces, which are available on all nodes
+
+* only use device passthroughs, which are available on all nodes
+
+If a VM or container cannot fully meet these requirements, it can still
+be possible to configure them as HA resources by encoding the deviations
+from these requirements as xref:ha_manager_rules[HA rules]. For example,
+if the device passthrough for an HA resource is only available to some
+of the cluster nodes, then the HA resource must be constrained to these
+cluster nodes by a strict
+xref:ha_manager_node_affinity_rules[node affinity rule].
+
 Management Tasks
 ----------------
 
-- 
2.47.3