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From "Dinesh S. Atreya (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-9607) Advance Hadoop Architecture (AHA) - HDFS Update
Date Mon, 25 Jan 2016 01:05:39 GMT

    [ https://issues.apache.org/jira/browse/HDFS-9607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15114620#comment-15114620
] 

Dinesh S. Atreya commented on HDFS-9607:
----------------------------------------

Konstantin,

First thank you for the positive comments regarding feasibility. Yes your assumption is essentially
correct: this JIRA is about random updates, random write-in-place, random read-write, specifically
random read-copy-write.

However, I want to be careful regarding random writes on the get go. Even though HDFS files
stores bytes, from a users perspective, these bytes could be finance data or personal contact
data or some customer order data etc., that the user may not want to get corrupted. Most often
this data will be read first before getting updated, hence *_random updates, random write-in-place,
random read-write, specifically random read-copy-write_* (unless the data is an append/insert
which HDFS already supports).

(Hence I am a little bit apprehensive regarding adding just one positional write method to
DFSOutputStream)

So semantically we want to propose *random updates* with *canWrite* checks that check against
the length that was read first. These checks can be relaxed as needed and provide random write
capabilities.

> Advance Hadoop Architecture (AHA) - HDFS Update
> -----------------------------------------------
>
>                 Key: HDFS-9607
>                 URL: https://issues.apache.org/jira/browse/HDFS-9607
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Dinesh S. Atreya
>
> Link to Umbrella JIRA
> https://issues.apache.org/jira/browse/HADOOP-12620 
> Provide capability to carry out in-place writes/updates. Only writes in-place are supported
where the existing length does not change.
> For example, "Hello World" can be replaced by "Hello HDFS!"
> See https://issues.apache.org/jira/browse/HADOOP-12620?focusedCommentId=15046300&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-15046300
for more details.



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