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From "Phabricator (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Mon, 06 Feb 2012 20:06:01 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201529#comment-13201529
] 

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

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

  I haven't thought about it quite enough, but is there any way to do this without leaking
the HFileSystem out to the rest of the code? As Ted pointed out, there are some somewhat public
interfaces that will probably get touched by that, and the number of places it has required
changes in unrelated test cases seems like a "code smell" to me.

  Maybe this could be a static cache somewhere, that given a FileSystem instance, it maintains
the un-checksumed equivalents thereof as weak references? Then the concept would be self-contained
within the HFile code, which up til now has been a fairly standalone file format.

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
>
>
> 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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