Merge "Spec: Add FibreChannel support to NetApp drivers"

specs/kilo/add-fibre-channel-support-to-netapp-drivers.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
+
+======================================
+NetApp Data ONTAP FibreChannel drivers
+======================================
+
+https://blueprints.launchpad.net/cinder/+spec/add-fibre-channel-support-to-
+netapp-drivers
+
+NetApp's Cinder volume drivers for Data ONTAP support iSCSI, and we are adding
+FibreChannel support as well.
+
+Problem description
+===================
+
+Cinder volume drivers must extend the protocol-specific subclass of
+VolumeDriver (i.e. ISCSIDriver or FibreChannelDriver).  The inheritance model
+employed by the NetApp iSCSI drivers is not conducive to adding FibreChannel
+support to their extant iSCSI capability.
+
+Other vendors have moved common, protocol-agnostic driver code into library
+modules and called those from the actual driver modules, which then become
+very thin indirection layers.  NetApp will take this approach as well.
+
+Proposed change
+===============
+
+We will make the following changes:
+
+* Move all iSCSI Data ONTAP driver code into library modules (base class plus
+  subclasses for 7-mode and cluster-mode specializations).
+
+* Convert the driver modules for iSCSI (7-mode and cluster-mode) into thin
+  indirection layers.
+
+* Add corresponding FibreChannel driver modules that call (mostly) the same
+  logic in the library modules.
+
+* Enhance the libraries' handling of igroups and initiators to be multi-
+  initiator-aware, since FC HBAs typically report multiple host-side WWPNs to
+  Nova/Cinder.
+
+* Enhance the library modules to handle FC-specific attach/detach operations
+  in the same way as other FC drivers.  We will take full advantage of the
+  Zone Manager code in Cinder.
+
+* Enhance our unit tests to cover all the proposed changes, and continue the
+  multi-release process of moving NetApp's Cinder unit tests into the correct
+  directory structure.
+
+The refactoring needed in the iSCSI drivers to pave the way for FC drivers
+will be submitted first, followed by a separate submission to add the FC
+drivers themselves.
+
+Alternatives
+------------
+
+In addition to the library approach, we also considered building our drivers
+using Python mixins, which would eliminate the indirection layer in the driver
+modules.  The problem with mixins is that IDEs cannot follow references, and
+the mixins cannot be standalone modules since they need common data such as
+Cinder configuration objects.  We prototyped both approaches, but the library
+solution is much more convenient to work with.
+
+Data model impact
+-----------------
+
+None
+
+REST API impact
+---------------
+
+None
+
+Security impact
+---------------
+
+None
+
+Notifications impact
+--------------------
+
+None
+
+Other end user impact
+---------------------
+
+None
+
+Performance Impact
+------------------
+
+None
+
+Other deployer impact
+---------------------
+
+One new NetApp-specific config flag is required: netapp_partner_backend_name
+
+NetApp Data ONTAP (7-mode) storage controllers typically operate in HA pairs,
+and in a FibreChannel (FC) environment each controller presents LUNs from its
+partner into the FC fabric(s).  So the driver must be able to read the FC
+port info and LUN map info from not only the controller owning a LUN but also
+from its HA partner.  The added flag identifies the config file stanza for the
+HA partner (which is always its own Cinder backend).  This approach is much
+cleaner than duplicating all the partner connection details in each backend
+stanza.
+
+
+Developer impact
+----------------
+
+None
+
+
+Implementation
+==============
+
+Assignee(s)
+-----------
+
+Primary assignee:
+  Clinton Knight (cknight)
+
+Other contributors:
+  Rushil Chugh (rushil)
+
+
+Work Items
+----------
+
+* Set up FC dev/test environment.
+
+* Refactor drivers to move block storage code into reusable libraries.
+
+* Create FC driver modules for Data ONTAP (7-mode & cluster-mode).
+
+* Update & extend unit tests accordingly.
+
+
+Dependencies
+============
+
+* The refactoring to prepare for FC drivers was captured in a separate
+  blueprint: https://blueprints.launchpad.net/cinder/+spec/netapp-cinder-
+  driver-refactoring-phase-1
+
+
+Testing
+=======
+
+Running our existing tempest tests in the FC dev/test environment is the
+initial step to know the FC-specific changes in the driver libraries are
+working.  Regression tests in iSCSI environments will ensure nothing was
+broken.
+
+We are also building a CI system, which will be extended during Kilo to
+include running tempest in an FC environment.
+
+
+Documentation Impact
+====================
+
+What is the impact on the docs team of this change? Some changes might require
+donating resources to the docs team to have the documentation updated. Don't
+repeat details discussed above, but please reference them here.
+
+
+References
+==========
+
+* The FC implementation described above was informed by pre-existing FC
+  drivers from other vendors, most notably the HP/3PAR one.  A conversation
+  with Walter Boring was very helpful.
+