Add support for FICON attached ECKD volumes for Linux on System z
This spec describes required changes to support FICON attached ECKD volumes. Implements: blueprint linux-ficon-support Change-Id: Ib64b7d952b125445b0a38b693256987a2da8bfcb
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Stefan Amann
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specs/newton/linux-ficon-support.rst
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specs/newton/linux-ficon-support.rst
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..
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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================================================================
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Support ECKD volumes on Linux on System z
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================================================================
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https://blueprints.launchpad.net/cinder/+spec/linux-ficon-support
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FICON (Fibre Connection) is a Fibre-Channel FC-4 layer protocol. It is
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used on mainframes to attach ECKD volumes via Fibre-Channel.
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Several changes are needed in order to allow Cinder to
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manage FICON-based block storage on Linux on System z.
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Besides, support is to be added to the existing Cinder drivers
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for storage subsystems supporting ECKD (for example, IBM DS8000).
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Required support in Nova is described by a separate blueprint which is
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listed as a dependency below.
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Problem description
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===================
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FICON and FCP are Fibre-Channel FC-4 layer protocols. FICON uses a
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different scheme to address volumes, compared to FCP.
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* ECKD volumes are addressed by a Control Unit and Unit Address, rather
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than WWPN and LUN.
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* System z uses a different format for device file paths (ccw-based, rather
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than pci-based), similar to the file paths used for FCP on System z
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* ECKD volumes need to be set online and formatted before they can be
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used
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Use Cases
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=========
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Allow an end-user to create and manage Cinder block devices based upon
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FICON attached storage subsystems supporting the ECKD protocol.
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For example: create, delete, image deploy, snapshot, ..
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We will extend a Cinder driver for IBMs DS8000. Other vendors, such as
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EMC, Hitachi, or HP support ECKD, too. They are potential candidates.
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Proposed change
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===============
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Change code in os-brick to address these issues, dependent on a new
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protocol type of 'fibre_channel_eckd', provided by the driver
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For details, see section `Work Items`.
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Alternatives
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------------
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None
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Data model impact
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-----------------
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None
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REST API impact
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---------------
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None
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Security impact
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---------------
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None
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Notifications impact
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--------------------
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None
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Other end user impact
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---------------------
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None
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Performance Impact
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------------------
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None
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Other deployer impact
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---------------------
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None
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Developer impact
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----------------
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Platforms that support FICON/ECKD will need to implement this for their
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drivers.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignee:
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stefan-amann
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Other contributors:
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arecknag
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maiera
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Work Items
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----------
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In ``os-brick/initiator/connector.py``:
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* provide a new connector FibreChannelECKDConnector
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* connect_volume needs to enable interrupts for the volume and
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set the volume online. This is done by calling the new
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configure_eckd_device() function)
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* disconnect_volume needs to set the volume offline. This is done by
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calling the new deconfigure_eckd_device() function
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In ``os-brick/initiator/linuxeckd.py``:
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* Utility functions to set the volume online, validate it is formatted
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appropriately, and format it if required
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::
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def _is_online(self, device):
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"""
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Return True if device is online, else return False
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:param device: device id
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"""
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if os.access('/sys/bus/ccw/devices/%s/online' % device, os.R_OK):
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online_file = None
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try:
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online_file = open('/sys/bus/ccw/devices/%s/online' % device)
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value = online_file.readline()
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if value and value.strip() == '1':
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return True
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finally:
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if online_file:
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online_file.close()
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return False
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def _is_formatted(self, device):
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"""
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Return True if device is online, else return False
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:param device: device id
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"""
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if os.access('/sys/bus/ccw/devices/%s/status' % device, os.R_OK):
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formatted = None
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(out, _err) = self._execute('cat',
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'/sys/bus/ccw/devices/%s/status' % device,
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run_as_root=True,
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root_helper=self._root_helper)
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if out and out.strip() == 'unformatted':
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return False
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return True
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def format_eckd_volume(self, path):
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"""
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formats ECKD volume
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:param device: device path
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"""
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name = os.path.realpath(path)
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if name.startswith("/dev/"):
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format_cmd = 'dasdfmt -y -b 4096 -d ldl ' + name
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(out, _err) = self._execute(format_cmd, run_as_root=True,
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root_helper=self._root_helper)
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return True
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else:
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return False
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In ``os-brick/initiator/linuxfc.py``:
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* new class LinuxFibreChannelECKD
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::
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def configure_eckd_device(self, device_number):
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"""Add the eckd volume to the Linux configuration. """
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full_device_identifier = "0.0.%04x" % device_number
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eckd_device_command = ('cio_ignore', '-r',
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'%(dev_id)s' % {"dev_id": full_device_identifier})
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LOG.debug("issue cio_ignore for s390: %s", eckd_device_command)
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out, info = None, None
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try:
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out, info = self._execute('cio_ignore', '-r',
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'%(dev_id)s' % {"dev_id": full_device_identifier},
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run_as_root=True,
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root_helper=self._root_helper)
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except putils.ProcessExecutionError as exc:
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LOG.warning(_LW("cio_ignore call for s390 failed exit"
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" %(code)s, stderr %(stderr)s"),
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{'code': exc.exit_code, 'stderr': exc.stderr})
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eckd_device_command = ('chccwdev', '-e',
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'%(dev_id)s' % {"dev_id": full_device_identifier})
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LOG.debug("add ECKD command for s390: %s", eckd_device_command)
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out, info = None, None
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try:
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out, info = self._execute('chccwdev', '-e',
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'%(dev_id)s' % {"dev_id": full_device_identifier},
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run_as_root=True,
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root_helper=self._root_helper)
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except putils.ProcessExecutionError as exc:
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LOG.warning(_LW("add ECKD call for s390 failed exit"
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" %(code)s, stderr %(stderr)s"),
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{'code': exc.exit_code, 'stderr': exc.stderr})
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def deconfigure_eckd_device(self, device_number):
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"""Remove the eckd volume from the Linux configuration. """
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LOG.debug("Deconfigure ECKD volume: device_number=%(device_num)s ",
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{'device_num': device_number})
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full_device_identifier = "0.0.%04x" % device_number
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eckd_device_command = ('chccwdev', '-d',
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'%(dev_id)s' % {"dev_id": full_device_identifier})
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LOG.debug("remove ECKD command for s390: %s", eckd_device_command)
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out, info = None, None
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try:
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out, info = self._execute('chccwdev', '-d',
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'%(dev_id)s' % {"dev_id": full_device_identifier},
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run_as_root=True,
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root_helper=self._root_helper)
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except putils.ProcessExecutionError as exc:
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LOG.warning(_LW("remove ECKD call for s390 failed exit"
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" %(code)s, stderr %(stderr)s"),
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{'code': exc.exit_code, 'stderr': exc.stderr})
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Adaptations to volume.filters to allow the new commands to be sent
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Cinder drivers need to report the Control Unit address, and Unit Address
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of the ECKD volume and set the driver_volume_type to 'fibre_channel_eckd'
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Any drivers wishing to support FICON will need to have CI reporting results
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from running against a FICON attached host.
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Dependencies
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============
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Nova blueprint to add support for ECKD for Linux on System z. The blueprint
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can be found here:
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https://blueprints.launchpad.net/nova/+spec/linux-ficon-support
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Testing
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=======
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Unit test:
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* Unit tests will be added and performed on System z, as well as
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Intel-based machines.
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CI environment:
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* We will provide a 3rd party CI environment for DS8000.
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Documentation Impact
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====================
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* We will update documentation as required.
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References
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==========
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* _`[1]` Linux on System z Device Driver book,
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http://public.dhe.ibm.com/software/dw/linux390/docu/l316dd25.pdf
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* _`[2]` Linux on System z,
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http://www.ibm.com/developerworks/linux/linux390/
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