Add service version for Antelope

Also did a bit of cleanup in the text message to tell *when* we need to bump
the min service version.
Given 2023.1 is our first SLURP release, we need to clarify the level of
support we now have for rolling upgrades.

Next cycle, we should update the min version to be Zed.

Change-Id: I2dd906f34118da02783bb7755e0d6c2a2b88eb5d

1 files changed, 13 insertions, 7 deletions

diff --git a/doc/source/admin/upgrades.rst b/doc/source/admin/upgrades.rst
index 00a714970b..61fd0cf258 100644
--- a/doc/source/admin/upgrades.rst
+++ b/doc/source/admin/upgrades.rst
@@ -41,21 +41,27 @@ Rolling upgrade process
 To reduce downtime, the compute services can be upgraded in a rolling fashion.
 It means upgrading a few services at a time. This results in a condition where
 both old (N) and new (N+1) nova-compute services co-exist for a certain time
-period. Note that, there is no upgrade of the hypervisor here, this is just
+period (or even N with N+2 upgraded nova-compute services, see below).
+Note that, there is no upgrade of the hypervisor here, this is just
 upgrading the nova services. If reduced downtime is not a concern (or lower
 complexity is desired), all services may be taken down and restarted at the
 same time.
 
 .. important::
 
-    Nova does not currently support the coexistence of N and N+2 or greater
-    :program:`nova-compute` or :program:`nova-conductor` services in the same
-    deployment. The `nova-conductor`` service will fail to start when a
-    ``nova-compute`` service that is older than the previous release (N-2 or
-    greater) is detected. Similarly, in a :doc:`deployment with multiple cells
+    As of OpenStack 2023.1 (Antelope), Nova supports the coexistence of N and
+    N-2 (Yoga) :program:`nova-compute` or :program:`nova-conductor` services in
+    the same deployment. The `nova-conductor`` service will fail to start when
+    a ``nova-compute`` service that is older than the support envelope is
+    detected. This varies by release and the support envelope will be explained
+    in the release notes. Similarly, in a :doc:`deployment with multiple cells
     </admin/cells>`, neither the super conductor service nor any per-cell
     conductor service will start if any other conductor service in the
-    deployment is older than the previous release.
+    deployment is older than the N-2 release.
+
+    Releases older than 2023.1 will only support rolling upgrades for a single
+    release difference between :program:`nova-compute` and
+    :program:`nova-conductor` services.
 
 #. Before maintenance window: