Add consistent-disk-identification spec

Change-Id: I67737aed7bf631c9610fca7f0ab52d97ca861bef
2016-02-09 21:27:14 +02:00 · 2016-02-09 21:27:14 +02:00 · 7453426a74
parent 99973fdd68
commit 7453426a74
1 changed files with 97 additions and 0 deletions
--- a/specs/consistent-disk-identification.rst
+++ b/specs/consistent-disk-identification.rst
@ -0,0 +1,97 @@
+..
+
+This work is licensed under a Creative Commons Attribution 3.0 Unported License.
+http://creativecommons.org/licenses/by/3.0/legalcode
+
+==============================
+Consistent disk identification
+==============================
+
+https://blueprints.launchpad.net/bareon/+spec/consistent-disk-identification
+
+Problem description
+===================
+
+Udev provides unstable disk naming (e.g. sda/sdb can switch through power cycles).
+Thus usage of these names in partitions schema is non-reliable.
+
+Bareon needs a predictable, repeatable, and consistent way of disk identification
+for the partitions schema. The method must be scalable and easy to maintain.
+For example, the "ID" should ideally be applicable to all BM servers of the
+same hardware configuration. UUIDs and S/Ns are unique to each physical server
+and therefore not usable for reasons of scalability and difficulty to maintain.
+
+Use cases:
+- Deploying a number of nodes, each node has 2 disks: 300 Gb SSD and 2Tb HDD.
+Disks may be discovered by udev in different order. Cray want’s all the nodes
+to be partitioned exactly the same - boot partition on the SSD, storage on HDD.
+
+
+Proposed change
+===============
+
+NOTE: This is a contribution of the feature developed within Cray OpenStack project.
+We will try to make a minimum changes to existing code.
+
+To provide a flexible and predictable way to point devices in partitions schema
+for Ironic data driver bareon adds support for the following disk identifiers:
+
+- SCSI address (bus position): 6:2:0:0
+- By path: disk/by-path/pci-0000:00:06.0-virtio-pci-virtio2 (exists already)
+- Name: vda. Eexists already. This reliable ID, should not be used when
+precise identification needed. Left for general use-cases.
+
+For this purpose the id property of the disk will be changed to include the
+type of identifier:
+
+    ::
+
+        {
+            "partitions":[
+                {
+                    "type": "disk",
+                    "id":{"type": "scsi", "value": "6:1:0:0"},
+                ...
+                }
+            ]
+        }
+
+Other examples of id are:
+
+    ::
+
+        "id":{"type": "path",
+              "value" : "disk/by-path/pci-0000:00:07.0-virtio-pci-virtio3"}
+
+        "id":{"type": "name", "value": "vda"}
+
+
+Alternatives
+------------
+
+To use existing nailgun schema (metadata) to identify disks (discuss if
+this is possible).
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+- max_lobur
+
+Milestones
+----------
+
+See blueprint ref above.
+
+Work Items
+----------
+
+- rebase onto Bareon master
+
+
+Dependencies
+============
+
+None.