Add policy-based partitioning spec

Change-Id: I1006fbdd6540b1e7d00ad33c366ce1eeda6180a8

specs/policy-based-partitioning.rst

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+..
+
+This work is licensed under a Creative Commons Attribution 3.0 Unported License.
+http://creativecommons.org/licenses/by/3.0/legalcode
+
+=========================
+Policy-based partitioning
+=========================
+
+https://blueprints.launchpad.net/bareon/+spec/policy-based-partitioning
+
+Problem description
+===================
+
+We need the ability to verify the disposition of existing partitions during
+deployment. Bareon agent should support the prevention of modification of
+existing partitions during deployment when requested by the user or
+administrator.
+
+Proposed change
+===============
+
+NOTE: This change is added with a standalone "Ironic" data driver.
+
+NOTE: This is a contribution of the feature developed within Cray OpenStack project.
+We will try to make a minimum changes to existing code.
+
+We introduce the new attribute in provision.json, called
+partitions_policy. This policy will control the way of how partitions are
+applied. The partitions_policy, working together with “keep_data” attribute
+of partition/lv will control the data retention. The policy can be either:
+
+* **verify**
+
+  - Do verification: Compare partitions schema with existing partitions on the
+    disk(disks). If there is an additional disk, not mentioned in schema
+    (unknown) - it is ignored.
+  - Do partitioning: partitions which do not have “keep_data” attribute are left
+    as is (keep_data attribute is true by default); partitions which have
+    “keep_data”:false attribute in schema are wiped;
+
+* **clean**
+
+    Ignore existing partitions on the disk(disks). Clean the disk and create
+    partitions according to the schema. If there is an additional disk, not
+    mentioned in schema (unknown) - it is ignored.
+
+For example:
+
+::
+
+    {
+      "partitions_policy": "<verify|clean>",
+      "partitions": [{
+             "type":"disk",
+             "id": ...,
+             "volumes":[
+                {
+                   "type":"partition",
+                   "id": …,
+                    # "keep_data": true - by default
+                },
+                {
+                   "id": …,
+                   "keep_data": false, # this partition will be wiped
+                   # (explicitly specified keep_data false here)
+                },
+              ],
+    }
+
+
+Alternatives
+------------
+
+There's already a keep_data flag in Nailgun driver, however it is impossible to
+verify HW partitions. So no alternatives to the current proposal.
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+- max_lobur
+
+Milestones
+----------
+
+See blueprint ref above.
+
+Work Items
+----------
+
+- Rebase onto Bareon master
+
+
+Dependencies
+============
+
+The code of this feature is on top of the following patches:
+
+- rsync image deployment
+- functional tests
+
+thus needs to be prosed after these.