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https://issues.apache.org/jira/browse/HADOOP-11828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15108177#comment-15108177
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Zhe Zhang commented on HADOOP-11828:
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I finished reviewing the patch and it LGTM overall. Given that this is a new
coder and doesn't modify existing code, I'm +1 on committing the latest patch
pending a fix on the license header and checkstyle issues, and the following
minor issue:
{code}
private HHUtil() {
// No called
}
{code}
For an util class with all static methods, we don't need a constructor.
Possible follow-on work and questions:
# The {{getPiggyBacksFromInput}} method is fairly complex and deserves a unit
test. A ASCII illustration would also be very helpful, similar to Figure 4 in
the Hitchhiker [paper |
http://eecs.berkeley.edu/~rashmikv/papers/Hitchhiker_SIGCOMM14.pdf].
# Could {{SUB_PACKET_SIZE}} be other than 2? If so, should we still keep it as
a variable?
# Maybe I'm missing something, but how do we guarantee the length of inputs
passed to {{performCoding}} is always {{numDataUnits * subPacketSize}}?
> Implement the Hitchhiker erasure coding algorithm
> -------------------------------------------------
>
> Key: HADOOP-11828
> URL: https://issues.apache.org/jira/browse/HADOOP-11828
> Project: Hadoop Common
> Issue Type: Sub-task
> Reporter: Zhe Zhang
> Assignee: jack liuquan
> Attachments: 7715-hitchhikerXOR-v2-testcode.patch,
> 7715-hitchhikerXOR-v2.patch, HADOOP-11828-hitchhikerXOR-V3.patch,
> HADOOP-11828-hitchhikerXOR-V4.patch, HADOOP-11828-hitchhikerXOR-V5.patch,
> HADOOP-11828-hitchhikerXOR-V6.patch, HADOOP-11828-hitchhikerXOR-V7.patch,
> HDFS-7715-hhxor-decoder.patch, HDFS-7715-hhxor-encoder.patch
>
>
> [Hitchhiker |
> http://www.eecs.berkeley.edu/~nihar/publications/Hitchhiker_SIGCOMM14.pdf] is
> a new erasure coding algorithm developed as a research project at UC
> Berkeley. It has been shown to reduce network traffic and disk I/O by 25%-45%
> during data reconstruction while retaining the same storage capacity and
> failure tolerance capability as RS codes. This JIRA aims to introduce
> Hitchhiker to the HDFS-EC framework, as one of the pluggable codec algorithms.
> The existing implementation is based on HDFS-RAID.
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