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https://issues.apache.org/jira/browse/HBASE-5074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13173012#comment-13173012
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Todd Lipcon commented on HBASE-5074:
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bq. One minor disadvantage of this approach is that checksums would be computed
twice, once by the hbase regionserver and once by the hdfs client. How bad is
this cpu overhead?
You mean on write? The native CRC32C implementation in HDFS trunk right now can
do somewhere around 6GB/sec - I clocked it at about 16% overhead compared to
the non-checksummed path a while ago. So I think overhead is fairly minimal.
bq. I am proposing that HBase disk format V3 have a 4 byte checksum for every
hbase block
4 byte checksum for 64KB+ of data seems pretty low. IMO we should continue to
do "chunked checksums" - maybe a CRC32 for every 1KB in the block. This allows
people to use larger block sizes without compromising checksum effectiveness.
The reason to choose chunked CRC32 over a wider hash is that CRC32 has a very
efficient hardware implementation in SSE4.2. Plus, we can share all the JNI
code already developed for Hadoop to calculate and verify these style of
checksums :)
> 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
>
> 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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