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From "Raghu Angadi (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-3981) Need a distributed file checksum algorithm for HDFS
Date Thu, 11 Sep 2008 00:44:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-3981?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12630050#action_12630050
] 

Raghu Angadi commented on HADOOP-3981:
--------------------------------------

Mostly minor  :

# DFSClient : {{sock.setSendBufferSize(DEFAULT_DATA_SOCKET_SIZE);}} is not required.
# DFSClient : {{LOG.warn("src=" + src, ie);}} is pretty vague. It could include datanode as
well.
# DFSClient : {{IOException("Fail to get block MD5 for block (=" + block)}} could be " {{IOException("Failed
to get block MD5 for " + block)}}
# I don't see much need for {{toByteArray()}} : -0.25.  at least it could move to some utils.
# 1MB buffer for {{MD5Hash.digest()}} seems too big. Any CPU benefits with MD5? This is another
utility function written as member. 

> Need a distributed file checksum algorithm for HDFS
> ---------------------------------------------------
>
>                 Key: HADOOP-3981
>                 URL: https://issues.apache.org/jira/browse/HADOOP-3981
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: Tsz Wo (Nicholas), SZE
>            Assignee: Tsz Wo (Nicholas), SZE
>         Attachments: 3981_20080909.patch, 3981_20080910.patch
>
>
> Traditional message digest algorithms, like MD5, SHA1, etc., require reading the entire
input message sequentially in a central location.  HDFS supports large files with multiple
tera bytes.  The overhead of reading the entire file is huge. A distributed file checksum
algorithm is needed for HDFS.

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