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doc: add document for rbd snapshot and clone
Added a document which contains the steps and RBD CLI commands we execute when we create a kubernetes snapshot, delete kubernetes snapshot, Restore a snapshot to a new PVC,Kubernetes volume cloning and kubernetes PVC deletion. Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>
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docs/design/proposals/rbd-snap-clone.md
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# Steps and RBD CLI commands for RBD snapshot and clone operations
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- [Steps and RBD CLI commands for RBD snapshot and clone operations](#steps-and-rbd-cli-commands-for-rbd-snapshot-and-clone-operations)
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- [Create a snapshot from PVC](#create-a-snapshot-from-pvc)
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- [steps to creating a snapshot](#steps-to-creating-a-snapshot)
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- [RBD CLI commands to create snapshot](#rbd-cli-commands-to-create-snapshot)
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- [Create PVC from a snapshot (datasource snapshot)](#create-pvc-from-a-snapshot-datasource-snapshot)
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- [steps to create a pvc from snapshot](#steps-to-create-a-pvc-from-snapshot)
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- [RBD CLI commands to create clone from snapshot](#rbd-cli-commands-to-create-clone-from-snapshot)
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- [Delete a snapshot](#delete-a-snapshot)
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- [steps to delete a snapshot](#steps-to-delete-a-snapshot)
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- [RBD CLI commands to delete a snapshot](#rbd-cli-commands-to-delete-a-snapshot)
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- [Delete a Volume (PVC)](#delete-a-volume-pvc)
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- [steps to delete a volume](#steps-to-delete-a-volume)
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- [RBD CLI commands to delete a volume](#rbd-cli-commands-to-delete-a-volume)
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- [Volume cloning (datasource pvc)](#volume-cloning-datasource-pvc)
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- [steps to create a Volume from Volume](#steps-to-create-a-volume-from-volume)
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- [RBD CLI commands to create a Volume from Volume](#rbd-cli-commands-to-create-a-volume-from-volume)
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This document outlines the command used to create RBD snapshot, delete RBD
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snapshot Restore RBD snapshot and Create New RBD image from RBD image.
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## Create a snapshot from PVC
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Refer [snapshot](https://kubernetes.io/docs/concepts/storage/volume-snapshots/)
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for more information realted to Volume cloning in kubernetes.
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### steps to creating a snapshot
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- Check if the parent image has more snapshots than the configured value, if
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its has more snapshot Add tasks to flatten all the temporary cloned images
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and return ResourceExhausted error message
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- Create a temporary snapshot from the parent image
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- Clone a new image from a temporary snapshot with options
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--rbd-default-clone-format 2 --image-feature layering,deep-flatten
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- Delete temporary snapshot created
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- Check the image chain depth, if the Softlimit is reached Add a task Flatten
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the cloned image and return success. If the depth is reached hardlimit Add a
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task Flatten the cloned image and return snapshot status ready as false
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### RBD CLI commands to create snapshot
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```bash
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[$] rbd snap ls <RBD image for src k8s volume> --all
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// If the parent has more snapshots than the configured `maxsnapshotsonimage`
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add backgound tasks to flatten the temporary cloned images( temporary cloned
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images name will be same as snapshot names)
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[$] ceph rbd task add flatten <RBD image for temporary snap images>
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[$] rbd snap create <RBD image for src k8s volume>@<random snap name>
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[$] rbd clone --rbd-default-clone-format 2 --image-feature
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layering,deep-flatten <RBD image for src k8s volume>@<random snap>
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<RBD image for temporary snap image>
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[$] rbd snap rm <RBD image for src k8s volume>@<random snap name>
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[$] rbd snap create <BD image for temporary snap image>@<random snap name>
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// check the depth,if the depth is greater than configured hardlimit add a
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// task to flatten the cloned image return snapshot status ready as false,
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// if the depth is greater than softlimit add a task to flatten the image
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// and return success
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[$] ceph rbd task add flatten <RBD image for temporary snap image>
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```
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## Create PVC from a snapshot (datasource snapshot)
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### steps to create a pvc from snapshot
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- Check the depth(n) of the cloned image if n>=(hardlimit -2) Add task to
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flatten the image and return ABORT (to avoid image leak)
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- Clone a new image from the snapshot with user-provided options
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### RBD CLI commands to create clone from snapshot
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```bash
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// check the depth,if the depth is greater than configured (hardlimit)
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// Add a task to value flatten the cloned image
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[$] ceph rbd task add flatten <RBD image for temporary snap image>
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[$] rbd clone --rbd-default-clone-format 2 --image-feature <k8s dst vol config>
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<RBD image for temporary snap image>@<random snap name>
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<RBD image for k8s dst vol>
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// check the depth,if the depth is greater than configured hardlimit add a task
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// to flatten the cloned image return ABORT error, if the depth is greater than
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// softlimit add a task to flatten the image and return success
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[$] ceph rbd task add flatten <RBD image for k8s dst vol>
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```
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## Delete a snapshot
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### steps to delete a snapshot
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- Delete temporary snapshot on temporary cloned image
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- Move the temporary cloned image to trash
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- Add task to remove the image from trash
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### RBD CLI commands to delete a snapshot
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```bash
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[$] rbd snap create <RBD image for temporary snap image>@<random snap name>
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[$] rbd trash mv <RBD image for temporary snap image>
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[$] ceph rbd task trash remove <RBD image for temporary snap image ID>
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```
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## Delete a Volume (PVC)
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With earlier implementation to delete the image we used to add a task to remove
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the image with new changes this cannot be done as the image may contains
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snapshots or linking.so we will be following below steps to delete an
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image(this will be applicable for both normal image and cloned image)
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### steps to delete a volume
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- Move the rbd image to trash
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- Add task to remove the image from trash
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### RBD CLI commands to delete a volume
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```bash
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1) rbd trash mv <image>
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2) ceph rbd task trash remove <image>
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```
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## Volume cloning (datasource pvc)
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Refer
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[volume-cloning](https://kubernetes.io/docs/concepts/storage/volume-pvc-datasource/)
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for more information realted to Volume cloning in kubernetes.
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### steps to create a Volume from Volume
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- Check the depth(n) of the cloned image if n>=((hard limit) -2) Add task to
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flatten the image and return about (to avoid image leak)
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- Create snapshot of rbd image
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- Clone the snapshot (temp clone)
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- Delete the snapshot
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- Snapshot the temp clone
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- Clone the snapshot (final clone)
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- Delete the snapshot
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### RBD CLI commands to create a Volume from Volume
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```bash
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// check the image depth of the parent image if flatten required add a
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// task to flatten image and return ABORT to avoid leak(same hardlimit and
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// softlimit check will be done)
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[$] ceph rbd task add flatten <RBD image for src k8s volume>
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[$] rbd snap create <RBD image for src k8s volume>@<random snap name>
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[$] rbd clone --rbd-default-clone-format 2 --image-feature
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layering,deep-flatten <RBD image for src k8s volume>@<random snap>
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<RBD image for temporary snap image>
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[$] rbd snap rm <RBD image for src k8s volume>@<random snap name>
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[$] rbd snap create <RBD image for temporary snap image>@<random snap name>
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[$] rbd clone --rbd-default-clone-format 2 --image-feature <k8s dst vol config>
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<RBD image for temporary snap image>@<random snap name>
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<RBD image for k8s dst vol>
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[$] rbd snap rm <RBD image for src k8s volume>@<random snap name>
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```
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