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https://issues.apache.org/jira/browse/HDFS-6677?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14061175#comment-14061175
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Haohui Mai commented on HDFS-6677:
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The patch looks good to me. +1
> Archival Storage: Change INodeFile and FSImage to support storage policy
> ------------------------------------------------------------------------
>
> Key: HDFS-6677
> URL: https://issues.apache.org/jira/browse/HDFS-6677
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: namenode
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h6677_20140714.patch
>
>
> Policy ID will be stored in INodeFile header with 4 bits which can support 16
> different storage policies. The number of bits for replication will be
> reduced from 16 bits to 12 bits which is still able to support up to 4095
> replicas. The number of bits for block size remains 48 bits. The memory
> usage of INodeFile remains unchanged.
> The storage policy IDs assigned to Hot, Warm and Cold policies are
> respectively 12, 8 and 4. These numbers are chosen with gaps so that future
> policies can be added in-between.
> We should make a corresponding change in FSImage.
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