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From "Gaurav Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1411) [Zebra] Can Zebra use HAR to reduce file/block count for namenode
Date Tue, 11 May 2010 17:43:41 GMT

    [ https://issues.apache.org/jira/browse/PIG-1411?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12866225#action_12866225

Gaurav Jain commented on PIG-1411:

-- 128 Files with 128 blocks of 128M each
-- 128K bytes taken in namenode

-- With 2GB HAR block size, 128 files --> 8 files ( 16 blocks in one HAR part file )
-- ~80K bytes taken in namenode
-- As total number of hdfs blocks will remain same of size 128M

So, its a  ~50% improvement in namespace which is not huge and needs to be evaluated against
performance loss of using HAR

WIth larger files, savings are not huge and performance should be taken into account before
using HAR  

With larger blocks size for both HAR or HDFS, further gains are expected. But those have their
own tradeoffs

> [Zebra] Can Zebra use HAR to reduce file/block count for namenode
> -----------------------------------------------------------------
>                 Key: PIG-1411
>                 URL: https://issues.apache.org/jira/browse/PIG-1411
>             Project: Pig
>          Issue Type: New Feature
>          Components: impl
>    Affects Versions: 0.8.0
>            Reporter: Gaurav Jain
>            Assignee: Gaurav Jain
>            Priority: Minor
>             Fix For: 0.8.0
> Due to column group structure,  Zebra can create extra files for namenode to remember.
That means namenode taking more memory for Zebra related files.
> The goal is to reduce the no of files/blocks
> The idea among various options is to use HAR ( Hadoop Archive ). Hadoop Archive reduces
the block  and file count by copying data from small files ( 1M, 2M ...) into a hdfs-block
of larger size. Thus, reducing the total no. of blocks and files.

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