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From "stack (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-1505) [performance] hfile should change how it reads from hdfs -- pread/seek+read -- dependent on recent history
Date Mon, 05 Oct 2009 21:21:31 GMT

    [ https://issues.apache.org/jira/browse/HBASE-1505?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12762378#action_12762378
] 

stack commented on HBASE-1505:
------------------------------

Turns out, we do seek and then read rather than pread.  I had it wrong way around.  We should
look into this.

> [performance] hfile should change how it reads from hdfs -- pread/seek+read -- dependent
on recent history
> ----------------------------------------------------------------------------------------------------------
>
>                 Key: HBASE-1505
>                 URL: https://issues.apache.org/jira/browse/HBASE-1505
>             Project: Hadoop HBase
>          Issue Type: Improvement
>            Reporter: stack
>             Fix For: 0.21.0
>
>
> hfile preads all the time at moment.  its good we do this when we want to up our random
reads.  but apparently pread involves open socket, seek, read, close socket whereas seek+read
could leave us aligned at next block to read and make for some savings.  hfile could have
a short memory and change how it pulls from hdfs dependent on recent history.

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