Konstantin Shvachko commented on HDFS-10301:

Besides, what is the last report? Reports can come to the NameNode in arbitrary 
order, can get lost, or can be repeated.
Looks like this is the last remaining issue. Can we please resolve it soon.

> BlockReport retransmissions may lead to storages falsely being declared 
> zombie if storage report processing happens out of order
> --------------------------------------------------------------------------------------------------------------------------------
>                 Key: HDFS-10301
>                 URL: https://issues.apache.org/jira/browse/HDFS-10301
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: namenode
>    Affects Versions: 2.6.1
>            Reporter: Konstantin Shvachko
>            Assignee: Vinitha Reddy Gankidi
>            Priority: Critical
>         Attachments: HDFS-10301.002.patch, HDFS-10301.003.patch, 
> HDFS-10301.004.patch, HDFS-10301.005.patch, HDFS-10301.006.patch, 
> HDFS-10301.007.patch, HDFS-10301.008.patch, HDFS-10301.009.patch, 
> HDFS-10301.01.patch, HDFS-10301.010.patch, HDFS-10301.011.patch, 
> HDFS-10301.012.patch, HDFS-10301.013.patch, HDFS-10301.014.patch, 
> HDFS-10301.branch-2.7.patch, HDFS-10301.branch-2.patch, 
> HDFS-10301.sample.patch, zombieStorageLogs.rtf
> When NameNode is busy a DataNode can timeout sending a block report. Then it 
> sends the block report again. Then NameNode while process these two reports 
> at the same time can interleave processing storages from different reports. 
> This screws up the blockReportId field, which makes NameNode think that some 
> storages are zombie. Replicas from zombie storages are immediately removed, 
> causing missing blocks.

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