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From "Zhe Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-7994) Detect if resevered EC Block ID is already used
Date Thu, 16 Apr 2015 22:38:00 GMT

    [ https://issues.apache.org/jira/browse/HDFS-7994?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14498894#comment-14498894
] 

Zhe Zhang commented on HDFS-7994:
---------------------------------

Sorry clicked Add by mistake. Continuing the comments:
# Seems to be a little weird to have a setter and a getter with the same name. Since the setter
is only called with true, maybe {{foundXxx}} instead of {{hasXxx}}?
# Since we plan to support EC with non-striping layout in phase II, non-EC blocks should be
"contiguous blocks". We can use an abbreviation of contiguous in naming
# The following can be a single if with _and_?
{code}
    if (!hasNonEcBlockUsingStripedID()){
      if (BlockIdManager.isStripedBlockID(block.getBlockId())) {
        hasNonEcBlockUsingStripedID(true);
      }
    }
{code}
# Maybe I'm missing something. But what if the block passed to {{addBlockCollectionWithCheck}}
is a striped block in the fsimage?

> Detect if resevered EC Block ID is already used
> -----------------------------------------------
>
>                 Key: HDFS-7994
>                 URL: https://issues.apache.org/jira/browse/HDFS-7994
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: namenode
>            Reporter: Tsz Wo Nicholas Sze
>            Assignee: Hui Zheng
>             Fix For: HDFS-7285
>
>         Attachments: HDFS-7994_001.patch, HDFS-7994_002.patch
>
>
> Since random block IDs were supported by some early version of HDFS, the block ID reserved
for EC blocks could be already used by some existing blocks in a cluster. During NameNode
startup, it detects if there are reserved EC block IDs used by non-EC blocks. If it is the
case, NameNode will do an additional blocksMap lookup when there is a miss in a blockGroupsMap
lookup.



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