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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HDFS-516) Low Latency distributed reads
Date Mon, 14 Sep 2009 16:08:57 GMT

    [ https://issues.apache.org/jira/browse/HDFS-516?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12755048#action_12755048
] 

Todd Lipcon commented on HDFS-516:
----------------------------------

I haven't had a chance to look over the patch as of yet, but I have one concern:

Is there a plan for deprecation in the event that HDFS itself achieves similar performance?
I think having an entirely separate FS implementation that only differs in performance is
not a good idea longterm. Using this contrib project as an experimentation ground sounds great,
but I think long term we should focus on improving DistributedFileSystem's performance itself,
and not bifurcate the code into the "fast version that we dont really support because it's
contrib" and "slow version that we do".

I'll try to find a chance to look over the patch soon, but in the meantime do you have any
thoughts on the above?

> Low Latency distributed reads
> -----------------------------
>
>                 Key: HDFS-516
>                 URL: https://issues.apache.org/jira/browse/HDFS-516
>             Project: Hadoop HDFS
>          Issue Type: New Feature
>            Reporter: Jay Booth
>            Priority: Minor
>         Attachments: hdfs-516-20090912.patch
>
>   Original Estimate: 168h
>  Remaining Estimate: 168h
>
> I created a method for low latency random reads using NIO on the server side and simulated
OS paging with LRU caching and lookahead on the client side.  Some applications could include
lucene searching (term->doc and doc->offset mappings are likely to be in local cache,
thus much faster than nutch's current FsDirectory impl and binary search through record files
(bytes at 1/2, 1/4, 1/8 marks are likely to be cached)

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