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HDFS-8852. HDFS architecture documentation of version 2.x is outdated about append write support. Contributed by Ajith S. 

(cherry picked from commit fc509f66d8)
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Akira Ajisaka 2015-08-18 23:31:52 +09:00
parent 9ab89a9266
commit 38b344adfa
2 changed files with 4 additions and 1 deletions
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hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt
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@ -847,6 +847,9 @@ Release 2.7.2 - UNRELEASED
HDFS-8806. Inconsistent metrics: number of missing blocks with replication
factor 1 not properly cleared. (Zhe Zhang via aajisaka)
HDFS-8852. HDFS architecture documentation of version 2.x is outdated
about append write support. (Ajith S via aajisaka)
Release 2.7.1 - 2015-07-06
INCOMPATIBLE CHANGES

2
hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsDesign.md
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@ -73,7 +73,7 @@ Applications that run on HDFS have large data sets. A typical file in HDFS is gi
### Simple Coherency Model
HDFS applications need a write-once-read-many access model for files. A file once created, written, and closed need not be changed. This assumption simplifies data coherency issues and enables high throughput data access. A Map/Reduce application or a web crawler application fits perfectly with this model. There is a plan to support appending-writes to files in the future.
HDFS applications need a write-once-read-many access model for files. A file once created, written, and closed need not be changed except for appends and truncates. Appending the content to the end of the files is supported but cannot be updated at arbitrary point. This assumption simplifies data coherency issues and enables high throughput data access. A MapReduce application or a web crawler application fits perfectly with this model.
### "Moving Computation is Cheaper than Moving Data"