172 lines
4.3 KiB
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172 lines
4.3 KiB
ReStructuredText
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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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NFS Snapshots
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==========================================
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https://blueprints.launchpad.net/cinder/+spec/nfs-snapshots
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Add support for snapshots (create, delete, clone from) to the
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NFS volume driver, so that it is as functional as other
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Cinder drivers.
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Problem description
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===================
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The NFS driver does not support many features expected in a modern Cinder
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driver.
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* create snapshot
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* delete snapshot
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* clone from snapshot
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Use Cases
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=========
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Proposed change
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===============
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The basic model for how snapshots can be implemented here has been proven
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in the GlusterFS driver. The general idea here is to re-use that same
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model and much of the code for the NFS driver, which works the same as
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the GlusterFS driver in general.
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In Juno, most of the snapshot-related code was refactored into a
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RemoteFSSnapshot class.
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The NFS driver should inherit code from this base class (and probably
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make minor changes) to gain snapshot support.
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Alternatives
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------------
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No real alternative, baseline NFS servers do not have the ability to snapshot
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files. This method is already used in other Cinder drivers and works, so the
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only alternative is to decide we don't want snapshots for this driver.
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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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Nothing significant.
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initialize_connection will return additional fields specifying the format
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of the volume file so that Nova knows how to attach it properly.
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Security impact
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---------------
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None, see notes here.
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This change needs to be tested with the NFS security infrastructure added
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in Kilo to ensure nothing breaks and that all files before, after, and during
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snapshot operations have the expected permissions. There is no reason to
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expect problems here.
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In Juno a security concern related to qcow2 file handling was addressed.
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( https://bugs.launchpad.net/cinder/+bug/1350504 )
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This is now considered fixed from a security perspective as there are no
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known ways to exploit it, but is still being fixed in a more robust manner
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in the "Support storing volume format info" spec. This work is possible in
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parallel as there is no strict interdependency here.
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( https://review.openstack.org/#/c/103750/ )
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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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We do not yet support backups of qcow2-based volumes. (Unsure if targeted
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in Kilo elsewhere.)
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Performance Impact
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------------------
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The NFS driver needs to have a per-volume-id lock for operations that
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manipulate volume/snapshot data. This does not cause any performance
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regression in existing functionality and should not be a large concern
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in most scenarios when using snapshots.
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See https://review.openstack.org/#/c/106095/ (GlusterFS example)
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Other deployer impact
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---------------------
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New config option, nfs_qcow2_volumes, to specify if you would like to
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always create volume files as qcow2 images rather than raw.
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Developer impact
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----------------
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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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eharney and akerr (?)
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Other contributors:
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NetApp has indicated they will CI this driver. (bswartz)
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Work Items
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----------
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- Try to inherit RemoteFSSnapshot code into NFS driver.
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- Iterate on issues there.
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- Test security concerns.
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Dependencies
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============
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Storing volume format info: https://review.openstack.org/#/c/103750/
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- Not a strict dependency, and which lands first is not vital, but this
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effort also needs to land in Kilo along with this work and is strongly
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related.
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I will submit another spec addressing the snapshot API between Cinder and
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Nova which will be used here, but nothing there blocks this work.
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Testing
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=======
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Standard third-party CI of the NFS driver
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Consider testing this in-gate as a later effort
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Documentation Impact
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====================
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New config option, nfs_qcow2_volumes.
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References
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==========
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Original snapshot effort which this is based on:
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https://blueprints.launchpad.net/cinder/+spec/qemu-assisted-snapshots
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RemoteFS snapshot code refactoring, done to support this effort:
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https://review.openstack.org/#/c/106066/
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SMBFS volume driver, an example of another driver re-using this code:
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https://review.openstack.org/#/c/106046/
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