PendingReleaseNotes: note CRUSH and hashpspool default changes

Signed-off-by: Sage Weil <[email protected]>

PendingReleaseNotes

@@ -1,3 +1,27 @@
+v0.74
+~~~~~
+
+- We now default to the 'bobtail' CRUSH tunable values that are first supported
+  by Ceph clients in bobtail (v0.48) and Linux kernel version v3.9.  If you
+  plan to access a newly created Ceph cluster with an older kernel client, you
+  should use 'ceph osd crush tunables legacy' to switch back to the legacy
+  behavior.  Note that making that change will likely result in some data
+  movement in the system, so adjust the setting before populating the new
+  cluster with data.
+
+- We now set the HASHPSPOOL flag on newly created pools (and new
+  clusters) by default.  Support for this flag first appeared in
+  v0.64; v0.67 Dumpling is the first major release that supports it.
+  It is first supported by the Linux kernel version v3.9.  If you plan
+  to access a newly created Ceph cluster with an older kernel or
+  clients (e.g, librados, librbd) from a pre-dumpling Ceph release,
+  you should add 'osd pool default flag hashpspool = false' to the
+  '[global]' section of your 'ceph.conf' prior to creating your
+  monitors (e.g., after 'ceph-deploy new' but before 'ceph-deploy mon
+  create ...').
+
+
+
 v0.73
 ~~~~~