Commit c9476f1b authored by Tomasz Kulasek's avatar Tomasz Kulasek Committed by Jim Harris
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doc/lvol: add diagrams to clone-snapshot doc 



Change-Id: I1cac468c58d84ed03bb646b8485e92fdb533049e
Signed-off-by: default avatarTomasz Kulasek <tomaszx.kulasek@intel.com>
Reviewed-on: https://review.gerrithub.io/413254


Reviewed-by: default avatarTomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: default avatarDaniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: default avatarJim Harris <james.r.harris@intel.com>
Tested-by: default avatarSPDK Automated Test System <sys_sgsw@intel.com>
parent 8580daa1

doc/img/lvol_clone_snapshot_read.svg

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doc/img/lvol_clone_snapshot_write.svg

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doc/lvol.md

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@@ -33,6 +33,13 @@ By default lvol bdevs claim part of lvol store equal to their set size. When thi 
Logical volumes support snapshots and clones functionality. User may at any given time create snapshot of existing logical volume to save a backup of current volume state.

When creating snapshot original volume becomes thin provisioned and saves only incremental differences from its underlying snapshot. This means that every read from unallocated cluster is actually a read from the snapshot and

every write to unallocated cluster triggers new cluster allocation and data copy from corresponding cluster in snapshot to the new cluster in logical volume before the actual write occurs.



The read operation is performed as shown in the diagram below:

![Reading cluster from clone](lvol_clone_snapshot_read.svg)



The write operation is performed as shown in the diagram below:

![Writing cluster to the clone](lvol_clone_snapshot_write.svg)



User may also create clone of existing snapshot that will be thin provisioned and it will behave in the same way as logical volume from which snapshot is created.

There is no limit of clones and snapshots that may be created as long as there is enough space on logical volume store. Snapshots are read only. Clones may be created only from snapshots.