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Posted to common-commits@hadoop.apache.org by in...@apache.org on 2016/10/03 22:58:54 UTC
[41/57] [abbrv] hadoop git commit: HDFS-10910. HDFS Erasure Coding
doc should state its currently supported erasure coding policies. Contributed
by Yiqun Lin.
HDFS-10910. HDFS Erasure Coding doc should state its currently supported erasure coding policies. Contributed by Yiqun Lin.
Project: http://git-wip-us.apache.org/repos/asf/hadoop/repo
Commit: http://git-wip-us.apache.org/repos/asf/hadoop/commit/ee33a022
Tree: http://git-wip-us.apache.org/repos/asf/hadoop/tree/ee33a022
Diff: http://git-wip-us.apache.org/repos/asf/hadoop/diff/ee33a022
Branch: refs/heads/HDFS-10467
Commit: ee33a02234511ac69c1e491fd38490a141ec907e
Parents: 2ab1ef1
Author: Wei-Chiu Chuang <we...@apache.org>
Authored: Fri Sep 30 12:48:11 2016 -0700
Committer: Wei-Chiu Chuang <we...@apache.org>
Committed: Fri Sep 30 12:48:11 2016 -0700
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.../hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)
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http://git-wip-us.apache.org/repos/asf/hadoop/blob/ee33a022/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md
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diff --git a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md
index 9066a15..76c1b3a 100644
--- a/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md
+++ b/hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md
@@ -59,9 +59,9 @@ Architecture
1. _Read the data from source nodes:_ Input data is read in parallel from source nodes using a dedicated thread pool.
Based on the EC policy, it schedules the read requests to all source targets and reads only the minimum number of input blocks for reconstruction.
- 1. _Decode the data and generate the output data:_ New data and parity blocks are decoded from the input data. All missing data and parity blocks are decoded together.
+ 2. _Decode the data and generate the output data:_ New data and parity blocks are decoded from the input data. All missing data and parity blocks are decoded together.
- 1. _Transfer the generated data blocks to target nodes:_ Once decoding is finished, the recovered blocks are transferred to target DataNodes.
+ 3. _Transfer the generated data blocks to target nodes:_ Once decoding is finished, the recovered blocks are transferred to target DataNodes.
* **ErasureCoding policy**
To accommodate heterogeneous workloads, we allow files and directories in an HDFS cluster to have different replication and EC policies.
@@ -69,10 +69,9 @@ Architecture
1. _The ECSchema:_ This includes the numbers of data and parity blocks in an EC group (e.g., 6+3), as well as the codec algorithm (e.g., Reed-Solomon).
- 1. _The size of a striping cell._ This determines the granularity of striped reads and writes, including buffer sizes and encoding work.
+ 2. _The size of a striping cell._ This determines the granularity of striped reads and writes, including buffer sizes and encoding work.
- Currently, HDFS supports the Reed-Solomon and XOR erasure coding algorithms. Additional algorithms are planned as future work.
- The system default scheme is Reed-Solomon (6, 3) with a cell size of 64KB.
+ There are three policies currently being supported: RS-DEFAULT-3-2-64k, RS-DEFAULT-6-3-64k and RS-LEGACY-6-3-64k. All with default cell size of 64KB. The system default policy is RS-DEFAULT-6-3-64k which use the default schema RS_6_3_SCHEMA with a cell size of 64KB.
Deployment
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