2263701157
In addition, moving specs from Kilo into Liberty that belong to blueprints that were not completed. Change-Id: Ibabce077579742b237a8cdb577414cc26228ec08
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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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Offload rbd's copy_volume_to_image function from host to ceph cluster
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=====================================================================
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Include the URL of your launchpad blueprint:
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https://blueprints.launchpad.net/cinder/+spec/optimze-rbd-copy-volume-to-image
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Offload rbd's copy_volume_to_image function from cinder-volume host to
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ceph cluster if cinder volume back end and glance storage back end are in
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the same ceph storage cluster.
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Problem description
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===================
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Suppose cinder volume back end and glance storage back end are in the same
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ceph storage cluster.
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Suppose the volume's capacity and data size in the following description
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are 1G.
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Suppose cinder volume back end use "volumes" pool, and glance storage back end
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use "images" pool.
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Currently upload-to-image routine works as follows:
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1. cinder use command "rbd export" to export the rbd image as a local file in
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cinder-volume host. Read 1G, and Write 1G.
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2. cinder call glance upload/update API to upload the exported local file to
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glance storage back end. Read 1G, and write 1G.
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So when we upload a 1G volume to image, we would read 2G data and write 2G
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data. If we offload this function from cinder-volume host to ceph storage
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cluster, we may only need to read 1G data and write 1G data, which could
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reduce the half amount of data transmission compared to the current routine.
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Benefits:
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* Reduce the read/write cost of rbd's copy_volume_to_image function,
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especially when the volume's capacity and data size are big.
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* Reduce the IO pressure on cinder-volume host when doing the
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copy_volume_to_image operation.
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Use Cases
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=========
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Proposed change
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===============
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By offload rbd's copy_volume_to_image function from host to ceph cluster
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, we need to do the following changes.
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* Check whether cinder volume back end and glance storage back end are in the
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same ceph storage cluster or not.
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* If not, keep the current work routine not change.
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* If yes, use rbd.Image.copy(dest_ioctx, dest_name) function to copy volume
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from one pool to another pool because cinder volume back end and glance
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storage back end always use different ceph pools.
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Alternatives
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------------
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Solution A: use rbd.Image.copy(dest_ioctx, dest_name) function to offload
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rbd's copy_volume_to_image function from host to ceph cluster.
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Solution B: use ceph's functions of clone image and flatten clone image to
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offload rbd's copy_volume_to_image function from host to ceph cluster. It
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contains the following steps.
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* Create a volume snapshot snap_a and protect the snapshot snap_a.
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* Clone a child image image_a of snap_a.
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* Flatten the child image image_a, and snap_a has not been depended on.
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* Unprotect the snapshot snap_a and delete it.
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Using a volume created based on "cirros-0.3.0-x86_64-disk" to show
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the time-consuming between solution A and solution B.
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* [Common]Create a volume based on image "cirros-0.3.0-x86_64-disk".
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::
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root@devaio:/home# cinder list
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+--------------------------------------+-----------+------+------+
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| ID | Status | Name | Size |
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+--------------------------------------+-----------+------+------+
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| 3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8 | available | None | 1 |
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+--------------------------------------+-----------+------+------+
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* [Solution-A-step-1]Copy
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8 from "volumes" pool to
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"images" pool.
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::
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root@devaio:/home# time rbd cp
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8 images/test
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Image copy: 100% complete...done.
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real 0m3.687s
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user 0m1.136s
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sys 0m0.557s
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* [Solution-B-step-1]Create a snapshot of volume
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3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8 and protect it.
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::
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root@devaio:/home# time rbd snap create --pool volumes --image
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volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8 --snap image_test
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real 0m3.152s
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user 0m0.018s
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sys 0m0.013s
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root@devaio:/home# time rbd snap protect
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test
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real 0m3.043s
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user 0m0.016s
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sys 0m0.012s
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* [Solution-B-step-2]Do clone operation on
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test.
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::
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root@devaio:/home# time rbd clone
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test
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images/snapshot_clone_image_test
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real 0m0.102s
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user 0m0.020s
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sys 0m0.016s
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* [Solution-B-step-3]Flatten the clone image images/snapshot_clone_image_test.
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::
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root@devaio:/home# time rbd flatten images/snapshot_clone_image_test
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Image flatten: 100% complete...done.
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real 0m10.228s
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user 0m1.375s
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sys 0m0.443s
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* [Solution-B-step-4]Unprotect the snap
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test.
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::
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root@devaio:/home# time rbd snap unprotect
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test
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real 0m0.064s
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user 0m0.019s
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sys 0m0.015s
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* [Solution-B-step-5]Delete the no dependency snap
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test.
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::
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root@devaio:/home# time rbd snap rm
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volumes/volume-3d6e5781-e3ac-4106-bfed-0aa0dd3af1f8@image_test
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real 0m0.235s
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user 0m0.017s
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sys 0m0.013s
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By the above test result of solution A and solution B, solution A needs
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(real:0m3.687s, user:0m1.136s, sys:0m0.557s) to finish the volume copy
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operation and solution B needs (real:0m16.824s, user:0m1.465s, sys:0m0.512s)
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to do that. So using solution A to offload rbd's copy_volume_to_image function
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from host to ceph cluster.
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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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Offload rbd's copy_volume_to_image function from host to ceph cluster could
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make full use of ceph's inherent data copy feature and the hardware capacity
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of ceph storage cluster to expedite the volume data copy speed, reduce the
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amount of data transmission and reduce the IO load on cinder-volume host.
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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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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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ling-yun<zengyunling@huawei.com>
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Work Items
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----------
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* Implement code that mentioned in "Proposed change".
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Dependencies
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============
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Cinder volume back end and glance storage back end are in the same
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ceph storage cluster.
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Testing
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=======
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Both unit and Tempest tests need to be created to cover the code change that
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mentioned in "Proposed change" and ensure that Cinder copy volume to image
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feature works well while introducing the feature of offload rbd's
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copy_volume_to_image function from host to ceph cluster.
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Documentation Impact
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====================
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None
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References
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==========
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None
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