[
https://issues.apache.org/jira/browse/HADOOP-11828?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15110481#comment-15110481
]
jack liuquan commented on HADOOP-11828:
---------------------------------------
Hi [~zhz],
Thanks for your review!
bq.For an util class with all static methods, we don't need a constructor.
I add a private constructor for checkstyle issue, just reference to code of
{{DumpUtil}} class in {{rawcoder}}
bq.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 .
Although {{getPiggyBacksFromInput }} is fairly complex, there only one running
branch in it. I think current unit test cases are good to cover it. I will add
a ASCII illustration for it.
bq.3.Maybe I'm missing something, but how do we guarantee the length of inputs
passed to performCoding is always numDataUnits * subPacketSize?
As Rashmi said, subPacketSize is always 2 in Hitchhiker. I think we can
guarantee it when we preparing block chunks.
> 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.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
