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Date: Wed, 22 Feb 2012 20:11:55 +0000 (UTC)
From: "Phabricator (Commented) (JIRA)" <jira@apache.org>
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Subject: [jira] [Commented] (HBASE-5074) support checksums in HBase block
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    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13213959#comment-13213959 ] 

Phabricator commented on HBASE-5074:
------------------------------------

dhruba has commented on the revision "[jira] [HBASE-5074] Support checksums in HBase block cache".

  > Ok. So, two readers. Our file count is going to go up?

  The file count should not go up. We still do the same number of ios to hdfs, so the number of concurrent IOs on a datanode should still be the same, so the number of xceivers on the datanode should not be adversely affected by this patch. Please let me know if I am missing something here.

REVISION DETAIL
  https://reviews.facebook.net/D1521

                
> support checksums in HBase block cache
> --------------------------------------
>
>                 Key: HBASE-5074
>                 URL: https://issues.apache.org/jira/browse/HBASE-5074
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: dhruba borthakur
>            Assignee: dhruba borthakur
>         Attachments: D1521.1.patch, D1521.1.patch, D1521.2.patch, D1521.2.patch, D1521.3.patch, D1521.3.patch, D1521.4.patch, D1521.4.patch, D1521.5.patch, D1521.5.patch, D1521.6.patch, D1521.6.patch, D1521.7.patch, D1521.7.patch, D1521.8.patch, D1521.8.patch
>
>
> The current implementation of HDFS stores the data in one block file and the metadata(checksum) in another block file. This means that every read into the HBase block cache actually consumes two disk iops, one to the datafile and one to the checksum file. This is a major problem for scaling HBase, because HBase is usually bottlenecked on the number of random disk iops that the storage-hardware offers.

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