Neil Ferguson created HBASE-7217:
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Summary: 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
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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