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From "dhruba borthakur (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1700) Append to files in HDFS
Date Fri, 30 Nov 2007 05:38:44 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1700?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12547003
] 

dhruba borthakur commented on HADOOP-1700:
------------------------------------------

Thanks Ruyue for your comments.

0. Regarding your comment about using a sequential block-id, instead of a random block-id:
How do we uprade existing clusters? An existing cluster can have huge number of already allocated
blocks.

1. Your comment about Point 1 makes sense. i will update the document.

2. Regarding Point 2: a file typically has few blocks, ranging from somewhere between 2 to
10 blocks.  I like your proposal to optimize transaction logging, especially when the number
of blocks in a file are huge. Is it possible to consider it as an enhancement and implement
it after implementing HDFS Apends? Won't the system be simpler if we avoid this optimization
at first go and then once HDFS Append is committed, then we can work on this optimization?

> Append to files in HDFS
> -----------------------
>
>                 Key: HADOOP-1700
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1700
>             Project: Hadoop
>          Issue Type: New Feature
>          Components: dfs
>            Reporter: stack
>         Attachments: Appends.doc, Appends.doc, Appends.html
>
>
> Request for being able to append to files in HDFS has been raised a couple of times on
the list of late.   For one example, see http://www.nabble.com/HDFS%2C-appending-writes-status-tf3848237.html#a10916193.
 Other mail describes folks' workarounds because this feature is lacking: e.g. http://www.nabble.com/Loading-data-into-HDFS-tf4200003.html#a12039480
(Later on this thread, Jim Kellerman re-raises the HBase need of this feature).  HADOOP-337
'DFS files should be appendable' makes mention of file append but it was opened early in the
life of HDFS when the focus was more on implementing the basics rather than adding new features.
 Interest fizzled.  Because HADOOP-337 is also a bit of a grab-bag -- it includes truncation
and being able to concurrently read/write -- rather than try and breathe new life into HADOOP-337,
instead, here is a new issue focused on file append.  Ultimately, being able to do as the
google GFS paper describes -- having multiple concurrent clients making 'Atomic Record Append'
to a single file would be sweet but at least for a first cut at this feature, IMO, a single
client appending to a single HDFS file letting the application manage the access would be
sufficent.

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