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https://issues.apache.org/jira/browse/HDFS-6702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14069809#comment-14069809
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Arpit Agarwal commented on HDFS-6702:
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bq. If we choose (a) then the index of targets and targetStorageTypes won't be
matched in the receiver side since targets[1..n-1] becomes targets[0..n-2] and
targetStorageTypes[0..n-1] remains targetStorageTypes[0..n-1], i.e.
targetStorageTypes[0] is for the first DN, targetStorageTypes[1] is for the
second DN and so on but targets[0] is for the second DN, targets[1] is for the
third DN and so on.
Okay I got it, this trick avoids special case code in {{writeBlock}}. Would you
consider adding a short comment explaining this?
bq. It is an two-dimensional array, which is similar to targetStorageUuids or
targets in BlockCommandProto.
Got it thanks.
+1
> DFSClient should create blocks using StorageType
> -------------------------------------------------
>
> Key: HDFS-6702
> URL: https://issues.apache.org/jira/browse/HDFS-6702
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode, hdfs-client
> Reporter: Tsz Wo Nicholas Sze
> Assignee: Tsz Wo Nicholas Sze
> Attachments: h6702_20140719.patch, h6702_20140721.patch,
> h6702_20140721b.patch
>
>
> When DFSClient asks NN for a new block (via addBlock), NN returns a
> LocatedBlock with storage type information. However, DFSClient does not use
> StorageType to create blocks with DN. As a result, the block replicas could
> possibly be created with a different storage type.
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