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https://issues.apache.org/jira/browse/HDFS-8432?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17155189#comment-17155189
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fengwu commented on HDFS-8432:
------------------------------
Hi, [~heliangjun] !
Can the datanode be downgraded successfull during your upgrade?
Found in my test roll downgrade from 3.1.3 to 2.7.2, namenode successful ，
but datanode failed （2.8+ successfully ）. because different datanode layout
versions is -56 in hdfs 2.7 .
{code:java}
// code placeholder
2020-07-06 14:45:01,313 WARN org.apache.hadoop.hdfs.server.common.Storage:
org.apache.hadoop.hdfs.server.common.IncorrectVersionException: Unexpected
version of storage directory /data/hadoop/dfs. Reported: -57. Expecting = -56.
2020-07-06 14:45:01,315 INFO org.apache.hadoop.hdfs.server.common.Storage: Lock
on /data/hadoop/dfs/in_use.lock acquired by nodename 21258@test-v03 2020-07-06
14:45:01,315 WARN org.apache.hadoop.hdfs.server.common.Storage:
org.apache.hadoop.hdfs.server.common.IncorrectVersionException: Unexpected
version of storage directory /data/hadoop/dfs. Reported: -57. Expecting = -56.
2020-07-06 14:45:01,315 FATAL org.apache.hadoop.hdfs.server.datanode.DataNode:
Initialization failed for Block pool <registering> (Datanode Uuid unassigned)
service to test-v01/10.110.228.21:8020. Exiting. java.io.IOException: All
specified directories are failed to load. at
org.apache.hadoop.hdfs.server.datanode.DataStorage.recoverTransitionRead(DataStorage.java:478)
at
org.apache.hadoop.hdfs.server.datanode.DataNode.initStorage(DataNode.java:1358)
at
org.apache.hadoop.hdfs.server.datanode.DataNode.initBlockPool(DataNode.java:1323)
at
org.apache.hadoop.hdfs.server.datanode.BPOfferService.verifyAndSetNamespaceInfo(BPOfferService.java:317)
at
org.apache.hadoop.hdfs.server.datanode.BPServiceActor.connectToNNAndHandshake(BPServiceActor.java:223)
at
org.apache.hadoop.hdfs.server.datanode.BPServiceActor.run(BPServiceActor.java:802)
at java.lang.Thread.run(Thread.java:748)
{code}
> Introduce a minimum compatible layout version to allow downgrade in more
> rolling upgrade use cases.
> ---------------------------------------------------------------------------------------------------
>
> Key: HDFS-8432
> URL: https://issues.apache.org/jira/browse/HDFS-8432
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: namenode, rolling upgrades
> Reporter: Chris Nauroth
> Assignee: Chris Nauroth
> Priority: Major
> Fix For: 2.8.0, 3.0.0-alpha1
>
> Attachments: HDFS-8432-HDFS-Downgrade-Extended-Support.pdf,
> HDFS-8432-branch-2.002.patch, HDFS-8432-branch-2.003.patch,
> HDFS-8432.001.patch, HDFS-8432.002.patch
>
>
> Maintain the prior layout version during the upgrade window and reject
> attempts to use new features until after the upgrade has been finalized.
> This guarantees that the prior software version can read the fsimage and edit
> logs if the administrator decides to downgrade. This will make downgrade
> usable for the majority of NameNode layout version changes, which just
> involve introduction of new edit log operations.
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