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https://issues.apache.org/jira/browse/HDFS-5526?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13826113#comment-13826113
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Tsz Wo (Nicholas), SZE commented on HDFS-5526:
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The problem is that ./current/VERSION is not rolled back. Below is a test case:
# format using v2.2.0
#* ./current/VERSION
{noformat}
#Mon Nov 18 18:26:32 PST 2013
storageID=DS-955224766-xx.xx.xx.xx-50010-1384827992929
clusterID=CID-7692ad34-b0d1-4e81-a08e-c714010a8355
cTime=0
storageType=DATA_NODE
layoutVersion=-47
{noformat}
#* ./previous
{noformat}
<not exist>
{noformat}
#* ./current/BP-1970701609-xx.xx.xx.xx-1384827972355/current/VERSION
{noformat}
#Mon Nov 18 18:26:33 PST 2013
namespaceID=737643680
cTime=0
blockpoolID=BP-1970701609-xx.xx.xx.xx-1384827972355
layoutVersion=-47
{noformat}
#* ./current/BP-1970701609-xx.xx.xx.xx-1384827972355/previous
{noformat}
<not exist>
{noformat}
# upgrade to trunk with layout version -48
#* ./current/VERSION
{noformat}
#Mon Nov 18 18:34:30 PST 2013
storageID=DS-955224766-xx.xx.xx.xx-50010-1384827992929
clusterID=CID-7692ad34-b0d1-4e81-a08e-c714010a8355
cTime=0
storageType=DATA_NODE
layoutVersion=-48
{noformat}
#* ./previous
{noformat}
<not exist>
{noformat}
#* ./current/BP-1970701609-xx.xx.xx.xx-1384827972355/current/VERSION
{noformat}
#Mon Nov 18 18:34:30 PST 2013
namespaceID=737643680
cTime=1384828466206
blockpoolID=BP-1970701609-xx.xx.xx.xx-1384827972355
layoutVersion=-48
{noformat}
#* ./current/BP-1970701609-xx.xx.xx.xx-1384827972355/previous/VERSION
{noformat}
#Mon Nov 18 18:26:33 PST 2013
namespaceID=737643680
cTime=0
blockpoolID=BP-1970701609-xx.xx.xx.xx-1384827972355
layoutVersion=-47
{noformat}
# rollback to -47 will fail with IncorrectVersionException
{code}
2013-11-18 18:41:56,420 FATAL datanode.DataNode (BPServiceActor.java:run(706))
- Initialization failed for block pool Block pool
BP-1970701609-xx.xx.xx.xx-1384827972355 (storage id ) service to
localhost/xx.xx.xx.xx:8020
org.apache.hadoop.hdfs.server.common.IncorrectVersionException: Unexpected
version of storage directory /Users/szetszwo/hadoop/_local_cluster/data1.
Reported: -48. Expecting = -47.
{code}
> Datanode cannot roll back to previous layout version
> ----------------------------------------------------
>
> Key: HDFS-5526
> URL: https://issues.apache.org/jira/browse/HDFS-5526
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Tsz Wo (Nicholas), SZE
> Priority: Blocker
>
> Current trunk layout version is -48.
> Hadoop v2.2.0 layout version is -47.
> If a cluster is upgraded from v2.2.0 (-47) to trunk (-48), the datanodes
> cannot start with -rollback. It will fail with IncorrectVersionException.
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