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Posted to issues@ozone.apache.org by "Sammi Chen (Jira)" <ji...@apache.org> on 2023/11/02 09:57:00 UTC

[jira] [Commented] (HDDS-9176) two client parallel perform commit with Hsync can cause dataloss

    [ https://issues.apache.org/jira/browse/HDDS-9176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17782087#comment-17782087 ] 

Sammi Chen commented on HDDS-9176:
----------------------------------

S3 allows concurrent write to the same object, the last committed one wins.  [https://docs.aws.amazon.com/AmazonS3/latest/userguide/Welcome.html#ConsistencyModel. |https://docs.aws.amazon.com/AmazonS3/latest/userguide/Welcome.html#ConsistencyModel]

While hsync is file action, from file system point of view, it can forbid two different clients writing to the same file concurrently. If one file request overrides another existing open file, then the existing open file needs to be deleted.

> two client parallel perform commit with Hsync can cause dataloss
> ----------------------------------------------------------------
>
>                 Key: HDDS-9176
>                 URL: https://issues.apache.org/jira/browse/HDDS-9176
>             Project: Apache Ozone
>          Issue Type: Sub-task
>            Reporter: Sumit Agrawal
>            Priority: Major
>
> 2 client performs commit with hsync feature,
>  * client 1 perform commit with Hsync with x block, key will be added in keyTable
>  * client 2 perform commit with Hsync with y block,
>  ** will overwrite previous key,
>  ** quota can be issue as previous key of client 1 is used to identify space usages delta
>  * client 1 perform final commit, will be treated as overwrite and remove blocks of client 2 data
>  * client 2 perform final commit, this will overwrite and remove blocks of client 1 data
> So in above flow, it can cause dataloss and quota will be not be counted properly for space usages.



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