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https://issues.apache.org/jira/browse/HBASE-7217?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack updated HBASE-7217:
-------------------------
Attachment: 7217.txt
Patch w/ Neil's fix (Move the 'HDFS Configuration' section under the 'HDFS'
section that comes later too).
> Documentation: Update section 11.5.1 to recommend that
> hbase.regionserver.checksum.verify is set
> ------------------------------------------------------------------------------------------------
>
> Key: HBASE-7217
> URL: https://issues.apache.org/jira/browse/HBASE-7217
> Project: HBase
> Issue Type: Improvement
> Components: documentation
> Affects Versions: 0.94.2
> Reporter: Neil Ferguson
> Priority: Minor
> Fix For: 0.96.0
>
> Attachments: 7217.txt
>
>
> When short-circuit reads are enabled (dfs.client.read.shortcircuit = true),
> reading with checksums enabled (dfs.client.read.shortcircuit.skip.checksum =
> false) follows a completely different, and much slower, path to reading with
> checksums disabled (BlockReaderLocal uses something called a "slow buffer",
> which is, unsurprisingly, slow). My tests show that this path is actually
> slower than having short-circuit reads disabled.
> Therefore, I think section 11.5.1 of the HBase documentation should recommend
> that hbase.regionserver.checksum.verify be set to true when using
> short-circuit reads. I'd suggest the following:
> "For optimal performance when short-circuit reads are enabled, it is
> recommended that HDFS checksums are disabled. To maintain data integrity with
> HDFS checksums disabled, HBase can be configured to write its own checksums
> into its datablocks and verify against these. See Section 11.4.9.
> "hbase.regionserver.checksum.verify".
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