doc/release/nautilus: proscribe minimum hammer tunables and straw2 on upgrade

Signed-off-by: Sage Weil <sage@redhat.com>
(cherry picked from commit 9b979a5c5d21d66bfd8ec69b5ad1d817ee9ecf78)

diff --git a/doc/rados/operations/balancer.rst b/doc/rados/operations/balancer.rst
index 120e29041fe153f5461454ddff23036cc1df0f3e..930ef0d8c2053b5c5af1b8e293f897796dc982d9 100644 (file)
--- a/doc/rados/operations/balancer.rst
+++ b/doc/rados/operations/balancer.rst
@@ -1,3 +1,6 @@
+
+.. _balancer:
+
 Balancer
 ========
 

diff --git a/doc/releases/nautilus.rst b/doc/releases/nautilus.rst
index d030907c9ab238baa7e4152adefe6c56d68997ca..b066778eec95a3f0979ef377e402e808747b994b 100644 (file)
--- a/doc/releases/nautilus.rst
+++ b/doc/releases/nautilus.rst
@@ -324,6 +324,28 @@ Instructions
 
 #. Verify the cluster is healthy with ``ceph health``.
 
+   If your CRUSH tunables are older than Hammer, Ceph will now issue a
+   health warning.  If you see a health alert to that effect, you can
+   revert this change with::
+
+     ceph config set mon mon_crush_min_required_version firefly
+
+   If Ceph does not complain, however, then we recommend you also
+   switch any existing CRUSH buckets to straw2, which was added back
+   in the Hammer release.  If you have any 'straw' buckets, this will
+   result in a modest amount of data movement, but generally nothing
+   too severe.::
+
+     ceph osd getcrushmap -o backup-crushmap
+     ceph osd crush set-all-straw-buckets-to-straw2
+
+   If there are problems, you can easily revert with::
+
+     ceph osd setcrushmap -i backup-crushmap
+
+   Moving to 'straw2' buckets will unlock a few recent features, like
+   the `crush-compat` :ref:`balancer <balancer>` mode added back in Luminous.
+
 #. To enable the new :ref:`v2 network protocol <msgr2>`, issue the
    following command::