[jira] [Created] (HDFS-5590) Sequential block ID may cause data loss when persistBlocks is set to false

["Jing Zhao (JIRA)" <ji...@apache.org>]

Jing Zhao created HDFS-5590:
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             Summary: Sequential block ID may cause data loss when persistBlocks is set to false
                 Key: HDFS-5590
                 URL: https://issues.apache.org/jira/browse/HDFS-5590
             Project: Hadoop HDFS
          Issue Type: Bug
    Affects Versions: 2.2.0
            Reporter: Jing Zhao
            Assignee: Jing Zhao


In a cluster with non-HA setup and dfs.persist.blocks set to false, the current sequential block ID may cause data loss in the following case:

# client creates file1 and requests a block from NN and get blk_id1_gs1
# client writes blk_id1_gs1 to DN
# NN is restarted and because persistBlocks is false, blk_id1_gs1 is not persisted in editlog
# another client creates file2 and NN will allocate a new block using the same block id blk_id1_gs1 since block ID and generation stamp are both increased sequentially.

Now we may have two versions (file1 and file2) of the blk_id1_gs1 (same id, same gs) in the system. It will case data loss.



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