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From "Todd Lipcon (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HADOOP-7370) Optimize pread on ChecksumFileSystem
Date Thu, 09 Jun 2011 07:53:58 GMT

     [ https://issues.apache.org/jira/browse/HADOOP-7370?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Todd Lipcon updated HADOOP-7370:

    Attachment: checksumfs-pread-0.20.txt

I was hacking on this against 0.20. It seems to have made a slight difference but I didn't
do any real benchmarking. This would have to be updated to trunk and then benchmarked before

> Optimize pread on ChecksumFileSystem
> ------------------------------------
>                 Key: HADOOP-7370
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7370
>             Project: Hadoop Common
>          Issue Type: Improvement
>          Components: fs
>            Reporter: Todd Lipcon
>            Assignee: Todd Lipcon
>            Priority: Minor
>         Attachments: checksumfs-pread-0.20.txt
> Currently the implementation of positional read in ChecksumFileSystem is verify inefficient
- it actually re-opens the underlying file and checksum file, then seeks and uses normal read.
Instead, it can push down positional read directly to the underlying FS and verify checksum.

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