[
https://issues.apache.org/jira/browse/HDFS-7285?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14391274#comment-14391274
]
Tsz Wo Nicholas Sze commented on HDFS-7285:
-------------------------------------------
Here is the list we discussed.
h2. Phase 1 – Basic EC features
- Support (6,3)-Reed-Solomon
- Read
-* from closed EC files
-* from files with some missing blocks
- Write
-* Write to 9 datanodes in parallel
-* Failure handling: continue writing with the remaining datanodes as long as
#existing datanodes >= 6.
- EC blocks reconstruction
-* Scheduled by NN like replication
-* Datanode executes block group reconstruction
- Block group lease recovery
-* Datanode executes lease recovery
-* Truncate at stripe group boundary
- NN changes
-* EC block group placement
-* EC zone
-* Safemode calculation
-* Quota
-* Block report processing
-* Snapshot
-* Fsck
-* Editlog/image
-* Block group support
-* EC file deletion
-* Decommission
-* Corrupted EC blocks
-* ID collision
- Balancer/Mover
-* Do not move EC blocks
- Documentation
- Testing
> 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: ECAnalyzer.py, ECParser.py, HDFS-7285-initial-PoC.patch,
> HDFSErasureCodingDesign-20141028.pdf, HDFSErasureCodingDesign-20141217.pdf,
> HDFSErasureCodingDesign-20150204.pdf, HDFSErasureCodingDesign-20150206.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)
