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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Created] (HDFS-7652) Process block reports for erasure coded blocks
Date Wed, 21 Jan 2015 20:07:34 GMT
Zhe Zhang created HDFS-7652:

             Summary: Process block reports for erasure coded blocks
                 Key: HDFS-7652
                 URL: https://issues.apache.org/jira/browse/HDFS-7652
             Project: Hadoop HDFS
          Issue Type: Sub-task
            Reporter: Zhe Zhang
            Assignee: Zhe Zhang

HDFS-7339 adds support in NameNode for persisting block groups. For memory efficiency, erasure
coded blocks under the striping layout are not stored in {{BlockManager#blocksMap}}. Instead,
entire block groups are stored in {{BlockGroupManager#blockGroups}}. When a block report arrives
from the DataNode, it should be processed under the block group that it belongs to. The following
naming protocol is used to calculate the group of a given block:
 * HDFS-EC introduces a hierarchical protocol to name blocks and groups:
 * Contiguous: {reserved block IDs | flag | block ID}
 * Striped: {reserved block IDs | flag | block group ID | index in group}
 * Following n bits of reserved block IDs, The (n+1)th bit in an ID
 * distinguishes contiguous (0) and striped (1) blocks. For a striped block,
 * bits (n+2) to (64-m) represent the ID of its block group, while the last m
 * bits represent its index of the group. The value m is determined by the
 * maximum number of blocks in a group (MAX_BLOCKS_IN_GROUP).

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