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https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13201619#comment-13201619
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Phabricator commented on HBASE-5074:
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todd has commented on the revision "[jira] [HBASE-5074] Support checksums in
HBase block cache".
Yea, I think the instanceof check and confining HFileSystem to be only within
the hfile package is much better.
I don't think it should be costly -- as you said, it's only when the reader
is created, which isn't on the hot code path, and instanceof checks are
actually quite fast. They turn into a simple compare of the instance's klassid
header against a constant, if I remember correctly.
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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