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https://issues.apache.org/jira/browse/HDDS-12924?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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ASF GitHub Bot updated HDDS-12924:
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    Labels: pull-request-available  (was: )

> Optimize DU for used space calculation
> --------------------------------------
>
>                 Key: HDDS-12924
>                 URL: https://issues.apache.org/jira/browse/HDDS-12924
>             Project: Apache Ozone
>          Issue Type: Sub-task
>          Components: Ozone Datanode
>            Reporter: Sumit Agrawal
>            Assignee: Sumit Agrawal
>            Priority: Major
>              Labels: pull-request-available
>
> h3. DU takes time when Running over disk having 10s TB of container data. 
> This will be slow operation.
>  
> *Sultion 1:* Run DU over non-ozone path
> Challenges: 
>  # Root path is not known for the device mounted on. So this needs extra 
> configuration.
>  # Permission problem: du will not count the space if permission is not there 
> on a certain path.
>  
> Based on the above concern, it's *not feasible* to do du over non-ozone path.
>  
> *Solution 2:* Run DU over meta path only (excluding container dir path)
> Ozone space usages includes Sum of:
>  # Sum of all Container data size as present in memory
>  # DU over volume path as current (excluding container path)
>  
> *Space not counted:*
>  * Ozone used size for duplicate containers are not counted (ignored during 
> startup for EC case)
>  * Ozone used size for containers corrupted are not counted, not deleted
>  * Container path meta files like container yaml, exported rocks db’s sst 
> files, are not counted, which might result in few GB of data in a large 
> cluster.
> These spaces will be added up to +non-ozone+ used space, and especially 
> un-accounted containers need to be cleaned up.
>  
> *Impact of inaccuracy of Used Space:*
>  * Used space in reporting (may be few GB as per above)
>  * Adjustment between Ozone available space and Rerved available space
> This inaccuracy does not have much impact over solution (as its present in 
> existing) and due to nature of “du” running async and parallel write 
> operation being in progress.
>  
> As part of this, can provide another strategy – “{*}OptimizedDU{*}” and 
> keeping old DU.
>  
> This solution seems to {*}provide a better approach{*}, as du is getting run 
> over smaller metadata size, and other used container data is computed from 
> memory.



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