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From "stack (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (HBASE-5074) support checksums in HBase block cache
Date Wed, 19 Sep 2012 20:09:09 GMT

     [ https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

stack updated HBASE-5074:
-------------------------

    Release Note: 
Adds hbase.regionserver.checksum.verify.  If hbase.regionserver.checksum.verify is set to
true, then hbase will read data and then verify checksums. Checksum verification inside hdfs
will be switched off.  If the hbase-checksum verification fails, then it will switch back
to using hdfs checksums for verifiying data that is being read from storage.  Also adds hbase.hstore.bytes.per.checksum
-- number of bytes in a newly created checksum chunk -- and hbase.hstore.bytes.per.checksum,
name of an algorithm that is used to compute checksums.

You will currently only see benefit if you have the local read short-circuit enabled -- see
http://hbase.apache.org/book.html#perf.hdfs.configs -- while HDFS-3429 goes unfixed.
    
> 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
>             Fix For: 0.94.0, 0.96.0
>
>         Attachments: 5074-0.94.txt, ASF.LICENSE.NOT.GRANTED--D1521.10.patch, ASF.LICENSE.NOT.GRANTED--D1521.10.patch,
ASF.LICENSE.NOT.GRANTED--D1521.11.patch, ASF.LICENSE.NOT.GRANTED--D1521.11.patch, ASF.LICENSE.NOT.GRANTED--D1521.12.patch,
ASF.LICENSE.NOT.GRANTED--D1521.12.patch, ASF.LICENSE.NOT.GRANTED--D1521.13.patch, ASF.LICENSE.NOT.GRANTED--D1521.13.patch,
ASF.LICENSE.NOT.GRANTED--D1521.14.patch, ASF.LICENSE.NOT.GRANTED--D1521.14.patch, ASF.LICENSE.NOT.GRANTED--D1521.1.patch,
ASF.LICENSE.NOT.GRANTED--D1521.1.patch, ASF.LICENSE.NOT.GRANTED--D1521.2.patch, ASF.LICENSE.NOT.GRANTED--D1521.2.patch,
ASF.LICENSE.NOT.GRANTED--D1521.3.patch, ASF.LICENSE.NOT.GRANTED--D1521.3.patch, ASF.LICENSE.NOT.GRANTED--D1521.4.patch,
ASF.LICENSE.NOT.GRANTED--D1521.4.patch, ASF.LICENSE.NOT.GRANTED--D1521.5.patch, ASF.LICENSE.NOT.GRANTED--D1521.5.patch,
ASF.LICENSE.NOT.GRANTED--D1521.6.patch, ASF.LICENSE.NOT.GRANTED--D1521.6.patch, ASF.LICENSE.NOT.GRANTED--D1521.7.patch,
ASF.LICENSE.NOT.GRANTED--D1521.7.patch, ASF.LICENSE.NOT.GRANTED--D1521.8.patch, ASF.LICENSE.NOT.GRANTED--D1521.8.patch,
ASF.LICENSE.NOT.GRANTED--D1521.9.patch, ASF.LICENSE.NOT.GRANTED--D1521.9.patch, D1521.10.patch,
D1521.10.patch, D1521.10.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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