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From "Tsz Wo (Nicholas), SZE (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4645) Move from randomly generated block ID to sequentially generated block ID
Date Wed, 03 Jul 2013 08:22:20 GMT

    [ https://issues.apache.org/jira/browse/HDFS-4645?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13698739#comment-13698739
] 

Tsz Wo (Nicholas), SZE commented on HDFS-4645:
----------------------------------------------

Some comments so far:
- Instead of "NEWGENSTAMP", let's call it something like "GENSTAMPv2" so that it is more extendable.
 We could support future changes of block id or the use of generation stamp.

- The name "maxGenerationStampForLegacyBlocks" may be confusion since it is not really a "max".
 "stampAtIdSwitch" sounds better.  Similarly, for get/setMaxSequentialBlockId.

- The block id and generation stamp code actually should be moved to the blockmanagement package.
 See if you want to move the code here.  Or we may do it later.

                
> Move from randomly generated block ID to sequentially generated block ID
> ------------------------------------------------------------------------
>
>                 Key: HDFS-4645
>                 URL: https://issues.apache.org/jira/browse/HDFS-4645
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: namenode
>    Affects Versions: 3.0.0
>            Reporter: Suresh Srinivas
>            Assignee: Arpit Agarwal
>         Attachments: editsStored, HDFS-4645.001.patch, HDFS-4645.002.patch, HDFS-4645.003.patch,
HDFS-4645.004.patch, HDFS-4645.005.patch, SequentialblockIDallocation.pdf
>
>
> Currently block IDs are randomly generated. This means there is no pattern to block ID
generation and no guarantees such as uniqueness of block ID for the life time of the system
can be made. I propose using SequentialNumber for block ID generation.

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