08dbaf42b1
I was asked to do this at the mid-cycle Change-Id: I5d57f7936a34907e73cf9f65bfe0790a2c92f020
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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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Libvirt: Support for attaching volumes via SMB
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==============================================
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https://blueprints.launchpad.net/nova/+spec/libvirt-smbfs-volume-support
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Currently, there are Libvirt volume drivers that support network-attached
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file systems such as Gluster of NFS. The purpose of this blueprint is adding
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support for attaching volumes hosted on a SMB share.
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Problem description
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===================
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SMB is another widely used protocol, especially in the Microsoft world. Its
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simplicity along with the big improvements that were introduced in SMB 3
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make this type of volume backend a very good alternative.
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SMB 3 brings features such as transparent failover, multichanneling using
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multiple NICs, encrypted communication, and RDMA. Newer versions of Samba
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are getting better support for the SMB 3 features, as well as supporting
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Active Directory membership.
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Use Cases
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----------
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Deployer will be able to attach block storage exported in the form of virtual
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disks on SMB shares to instances.
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Project Priority
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-----------------
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None
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Proposed change
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===============
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A new volume driver will be added in order to support attaching volumes
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hosted on SMB shares. The volume driver will have a similiar worflow with
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the NFS volume driver.
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The SMB volume driver will mount the SMB share on which a volume is hosted
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using credentials and other flags specified in the volume connection info.
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This feature will be backwards compatible, supporting older versions of SMB
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for simple tasks. It will support using any type of SMB share, including:
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- from Scale-Out file servers to basic Windows shares;
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- Linux SMB shares using Samba;
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- vendor specific hardware exporting SMB shares.
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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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The share credentials will be parsed in the volume connection info and used
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when mounting a SMB share.
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Also, the driver will support Active Directory integration (as long as the
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Samba version supports it) so that it will be able to use AD credentials.
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Note that as SAMBA does not support SELinux labelling, in order to be able
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to boot from a volume hosted on a SMB share, the virt_use_samba SELinux
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option will have to be enabled. This has security implications, as there
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will no longer be any security isolation between VM disk images.
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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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The deployer will be able to configure the path where the SMB shares will be
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mounted, as well as setting mount flags.
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Also, the Libvirt-qemu uid and gid will have to be specified as mount flags
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in order to support attaching volumes because of Libvirt trying to change
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the owner of the volume.
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In order to support SMB3 and AD integration, Samba 4.0 or later is required.
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Note that any version of Samba is supported by this driver but as older
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versions don't support AD integration, you won't be able to use AD based
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authentication. Also, in this case you must make sure that the SMB server you
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are trying to access has no restrictions on the SMB protocol version, being
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able to fall back to an older version.
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Developer impact
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----------------
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None
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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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<lpetrut@cloudbasesolutions.com>
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Other contributors:
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<gsamfira@cloudbasesolutions.com>
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Work Items
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----------
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Add support for mounting SMB shares.
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Provide support for local shares.
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Dependencies
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============
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None
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Testing
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=======
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This feature should be tested using one of the SMB Cinder Volume drivers
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already available. The existing Tempest tests along with the according unit
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tests should be enough for the moment in order to test this.
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While a CI is being considered, for the moment Tempest tests will be run
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periodically for this scenario.
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Documentation Impact
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====================
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Using the SMB backend will be documented.
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References
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==========
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Cinder SMB Driver blueprint:
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https://blueprints.launchpad.net/cinder/+spec/smbfs-volume-driver
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