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https://issues.apache.org/jira/browse/HDFS-6708?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16821969#comment-16821969
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Ewan Higgs commented on HDFS-6708:
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{quote}Daryn Sharp do you have an opinion on backwards compatibility for the
Writable case? I suspect older clients will ignore the extra fields harmlessly-
these should be framed in the RPC- but I haven't actually verified.{quote}
It looks like upgrading NN first means the fields are not harmlessly ignored,
presumably because the re-hash is not regenerated if the StorageType is ignored
(I haven't fully paged this topic back in).
Upgrading DNs first would allow the DN to understand any new message that the
NN might send. Documentation
[here|https://hadoop.apache.org/docs/stable/hadoop-project-dist/hadoop-hdfs/HdfsRollingUpgrade.html]
indicates that NN should be upgraded first.
> StorageType should be encoded in the block token
> ------------------------------------------------
>
> Key: HDFS-6708
> URL: https://issues.apache.org/jira/browse/HDFS-6708
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Affects Versions: 2.4.1
> Reporter: Arpit Agarwal
> Assignee: Ewan Higgs
> Priority: Major
> Fix For: 3.0.0-alpha4
>
> Attachments: HDFS-6708.0001.patch, HDFS-6708.0002.patch,
> HDFS-6708.0003.patch, HDFS-6708.0004.patch, HDFS-6708.0005.patch,
> HDFS-6708.0006.patch, HDFS-6708.0007.patch, HDFS-6708.0008.patch,
> HDFS-6708.0009.patch, HDFS-6708.0010.patch
>
>
> HDFS-6702 is adding support for file creation based on StorageType.
> The block token is used as a tamper-proof channel for communicating block
> parameters from the NN to the DN during block creation. The StorageType
> should be included in this block token.
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