ivampiresp/Spdk
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

doc/lvol: add diagrams to clone-snapshot doc

Browse Source 
Change-Id: I1cac468c58d84ed03bb646b8485e92fdb533049e
Signed-off-by: Tomasz Kulasek <tomaszx.kulasek@intel.com>
Reviewed-on: https://review.gerrithub.io/413254
Reviewed-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Reviewed-by: Daniel Verkamp <daniel.verkamp@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Tested-by: SPDK Automated Test System <sys_sgsw@intel.com>
This commit is contained in:
Tomasz Kulasek 2018-05-30 20:34:31 +02:00 committed by Jim Harris
parent 8580daa1ac
commit c9476f1b1b
3 changed files with 13 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
doc/img/lvol_clone_snapshot_read.svg Normal file
View File

File diff suppressed because one or more lines are too long
Side by Side

After

Width:  |  Height:  |  Size: 12 KiB

3
doc/img/lvol_clone_snapshot_write.svg Normal file
View File

File diff suppressed because one or more lines are too long
Side by Side

After

Width:  |  Height:  |  Size: 13 KiB

7
doc/lvol.md
View File

@ -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.