aswinshakil opened a new pull request, #5301:
URL: https://github.com/apache/ozone/pull/5301

   ## What changes were proposed in this pull request?
   
   The change proposes to add exclusive size for a snapshot. PR #5175 address 
Reference Size calculation for each Snapshot. I have linked a PDF in the JIRA 
explaining the design. I have summarized it below for future reference. A 
Snapshot has 4 size, 
   
   - Reference Size, it is explained here #5175 
   - Total Size - Refers to the sum of shared size and exclusive size of the 
snapshot. This is nothing but the bucket size during snapshot. 
   - Shared Size - Refers to data shared between snapshots. Hence this size 
can’t be quantified as data held by one snapshot but shared between 2 or more 
snapshots.
   - Exclusive Size - Refers to the data held only by that snapshot.
   
   ### Calculations: 
   ### Total Size
   We can get `Total Size` from the bucketInfo `omBucketInfo.getUsedBytes()`  
in the Snapshot. This gives the total size used by the snapshot. 
   
   **Note:** This give the size of the bucket **after** replication.
   ### Shared Size
   Once we get the Total Size and Exclusive Size we can calculate Shared Size.
   `Shared Size = Total Size - Exclusive Size`
   ### Exclusive Size
   To calculate `Exclusive Size` for current snapshot, Check the next snapshot 
`deletedTable` if the deleted key is **referenced** in current snapshot and 
**not referenced** in the previous snapshot then that key is exclusive to the 
current snapshot.
   
   ## Things to do in follow-up PRs
   
   - Expand `deletedDirTable` for all the snapshot.
   - Update the code to accommodate files moved to `deleteTable` and calculate 
Exclusive size. 
   
   ## What is the link to the Apache JIRA
   
   https://issues.apache.org/jira/browse/HDDS-7743
   
   ## How was this patch tested?
   
   Added New Unit Test and Integration test. 
   


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