Add support for File I/O Driver

This blueprint outlines the work to add support for File I/O based
ephemeral storage.
blueprint file-io-driver

Change-Id: Ia81d2e08b9cc609087aa31db20ec523eff73d0db

specs/pike/fileio_driver.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
+
+===============
+File I/O Driver
+===============
+
+https://blueprints.launchpad.net/nova-powervm/+spec/file-io-driver
+
+The PowerVM driver currently uses logical volumes for localdisk ephemeral
+storage.  This blueprint will add support for using file-backed disks as a
+localdisk ephemeral storage option.
+
+
+Problem description
+===================
+
+The PowerVM driver only supports logical volumes for localdisk ephemeral
+storage.  It does not currently support storage that is presented as a file.
+
+
+Use Cases
+---------
+
+* As a user, I want to have the instance ephemeral storage backed by a file.
+
+
+Proposed change
+===============
+
+Add nova_powervm/virt/powervm/disk/fileio.py.  This would extend the existing
+disk driver.  Use the DISK_DRIVER powervm conf option to select file I/O.
+Will utilize the nova.conf option instances_path.
+
+
+Alternatives
+------------
+
+None
+
+
+Security impact
+---------------
+
+None
+
+
+End user impact
+---------------
+
+None
+
+
+Performance Impact
+------------------
+
+Performance may change as the backing storage methods of VMs will be different.
+
+
+Deployer impact
+---------------
+
+The deployer must set the DISK_DRIVER conf option to fileio and ensure that
+the instances_path conf option is set in order to utilize the changes described
+in the blueprint.
+
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  tjakobs
+
+Other contributors:
+  None
+
+Work Items
+----------
+
+* Create a nova-powervm fileio driver.  Create associated UT.
+
+
+Dependencies
+============
+
+Novalink 1.0.0.5
+
+
+Testing
+=======
+
+* Unit tests for all code
+
+* Manual test will be driven using a File I/O ephemeral disk.
+
+
+Documentation Impact
+====================
+
+
+Will update the nova-powervm dev-ref to include File I/O as an additional
+ephemeral disk option.
+
+
+References
+==========
+
+None