[
https://issues.apache.org/jira/browse/HDFS-7285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14696880#comment-14696880
]
Vinayakumar B commented on HDFS-7285:
-------------------------------------
I have tried to rebase current {{HDFS-7285}} branch against the current trunk
using {{git rebase trunk}}. It was not smooth as expected. Since I did not
wanted to push the rebase directly onto {{HDFS-7285}}, created one more branch
{{HDFS-7285-REBASE}}. This branch is just for reference purpose.
The advantage of this is, it retained all the commits along with message,date
and author details, even after resolving conflicts. I skipped one commit
purposefully HDFS-8787 to be in sync with trunk. it was just rename of files.
other than this, no other commits got squashed.
There were 192 commits to be rebased against trunk, including the intermediate
merge conflict resolved commits. Since I couldnt edit each and every commit to
resolve compilation errors after each commit, resolved remaining compilation
errors at the end, with one more commit.
If anyone wants to verify, please checkout the branch HDFS-7285-REBASE. and can
compare against the Consolidated patch.
Since this is only for trying to check the possibility of rebase, I am not
saying this should be considered as final branch.
If everyone feels good to go like this approach, I could do some more detailed
rebase next week, ( may be verify the compilation after each commit ? Not sure
whether its possible to stop for each commit rebase)
-Thanks
> Erasure Coding Support inside HDFS
> ----------------------------------
>
> Key: HDFS-7285
> URL: https://issues.apache.org/jira/browse/HDFS-7285
> Project: Hadoop HDFS
> Issue Type: New Feature
> Reporter: Weihua Jiang
> Assignee: Zhe Zhang
> Attachments: Consolidated-20150707.patch,
> Consolidated-20150806.patch, Consolidated-20150810.patch, ECAnalyzer.py,
> ECParser.py, HDFS-7285-initial-PoC.patch,
> HDFS-7285-merge-consolidated-01.patch,
> HDFS-7285-merge-consolidated-trunk-01.patch,
> HDFS-7285-merge-consolidated.trunk.03.patch,
> HDFS-7285-merge-consolidated.trunk.04.patch,
> HDFS-EC-Merge-PoC-20150624.patch, HDFS-EC-merge-consolidated-01.patch,
> HDFS-bistriped.patch, HDFSErasureCodingDesign-20141028.pdf,
> HDFSErasureCodingDesign-20141217.pdf, HDFSErasureCodingDesign-20150204.pdf,
> HDFSErasureCodingDesign-20150206.pdf, HDFSErasureCodingPhaseITestPlan.pdf,
> fsimage-analysis-20150105.pdf
>
>
> Erasure Coding (EC) can greatly reduce the storage overhead without sacrifice
> of data reliability, comparing to the existing HDFS 3-replica approach. For
> example, if we use a 10+4 Reed Solomon coding, we can allow loss of 4 blocks,
> with storage overhead only being 40%. This makes EC a quite attractive
> alternative for big data storage, particularly for cold data.
> Facebook had a related open source project called HDFS-RAID. It used to be
> one of the contribute packages in HDFS but had been removed since Hadoop 2.0
> for maintain reason. The drawbacks are: 1) it is on top of HDFS and depends
> on MapReduce to do encoding and decoding tasks; 2) it can only be used for
> cold files that are intended not to be appended anymore; 3) the pure Java EC
> coding implementation is extremely slow in practical use. Due to these, it
> might not be a good idea to just bring HDFS-RAID back.
> We (Intel and Cloudera) are working on a design to build EC into HDFS that
> gets rid of any external dependencies, makes it self-contained and
> independently maintained. This design lays the EC feature on the storage type
> support and considers compatible with existing HDFS features like caching,
> snapshot, encryption, high availability and etc. This design will also
> support different EC coding schemes, implementations and policies for
> different deployment scenarios. By utilizing advanced libraries (e.g. Intel
> ISA-L library), an implementation can greatly improve the performance of EC
> encoding/decoding and makes the EC solution even more attractive. We will
> post the design document soon.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
