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From "dhruba borthakur (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-5074) support checksums in HBase block cache
Date Fri, 02 Mar 2012 19:01:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13221158#comment-13221158
] 

dhruba borthakur commented on HBASE-5074:
-----------------------------------------

The reason I kept the definition of CRC32C in the ChecksumType is essentially to reserve an
ordinal in the enum for this checksum algorithm in the future. We should just wait for Hadoop
2.0 to be released to get this feature (instead of copying it to hbase).

>  means that HFileV3 would start with minor version of 1.

I am suggesting that HFileV3 has nothing to do with minorVersions. HFileV3 can decide to support
minor version 0 or 1 or both. HFileV3 might not even use the HFileBlock format as we know
it, in which case the question is moot.
                
> 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, D1521.10.patch, D1521.10.patch, D1521.10.patch,
D1521.10.patch, D1521.10.patch, D1521.11.patch, D1521.11.patch, D1521.12.patch, D1521.12.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, D1521.9.patch, D1521.9.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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