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https://issues.apache.org/jira/browse/HDFS-10899?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16126845#comment-16126845
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Xiao Chen commented on HDFS-10899:
----------------------------------

Looked at the Daryn comment about edit log buffering and experimented.

For a {{SetXAttrOp}}, since re-encryption always updates the 1 encryption 
xattr, the size of one {{logEdit}} is between size 100 ~ 200 bytes (including 
the 17 bytes overhead which is always there). Default buffer size is 512KB 
non-configurable for both the 
[qjm|https://github.com/apache/hadoop/blob/branch-3.0.0-alpha4/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/qjournal/client/QuorumJournalManager.java#L99]
 and 
[fjm|https://github.com/apache/hadoop/blob/branch-3.0.0-alpha4/hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/FileJournalManager.java#L68],
 so the default batch size of 1000 is safe - as long as we {{logSync}} after 
each batch, which is current behavior.

As a safety check, I'm adding a scary warning if batch size is larger than 2000.

Also benchmarking to save our guts about NN throughput. Will post when all 
results are ready.

> Add functionality to re-encrypt EDEKs
> -------------------------------------
>
>                 Key: HDFS-10899
>                 URL: https://issues.apache.org/jira/browse/HDFS-10899
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>          Components: encryption, kms
>            Reporter: Xiao Chen
>            Assignee: Xiao Chen
>         Attachments: editsStored, HDFS-10899.01.patch, HDFS-10899.02.patch, 
> HDFS-10899.03.patch, HDFS-10899.04.patch, HDFS-10899.05.patch, 
> HDFS-10899.06.patch, HDFS-10899.07.patch, HDFS-10899.08.patch, 
> HDFS-10899.09.patch, HDFS-10899.10.patch, HDFS-10899.10.wip.patch, 
> HDFS-10899.11.patch, HDFS-10899.12.patch, HDFS-10899.13.patch, 
> HDFS-10899.wip.2.patch, HDFS-10899.wip.patch, Re-encrypt edek design doc.pdf, 
> Re-encrypt edek design doc V2.pdf
>
>
> Currently when an encryption zone (EZ) key is rotated, it only takes effect 
> on new EDEKs. We should provide a way to re-encrypt EDEKs after the EZ key 
> rotation, for improved security.



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