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HDFS-12927. Update erasure coding doc to address unsupported APIs. (Contributed by Lei (Eddy) Xu)

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Lei Xu 2017-12-15 10:20:29 -08:00
parent 1c15b1751c
commit 949be14b08
1 changed files with 5 additions and 2 deletions
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hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HDFSErasureCoding.md
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@ -220,11 +220,14 @@ Below are the details about each command.
Limitations
-----------
Certain HDFS file write operations, i.e., `hflush`, `hsync` and `append`,
Certain HDFS operations, i.e., `hflush`, `hsync`, `concat`, `setReplication`, `truncate` and `append`,
are not supported on erasure coded files due to substantial technical
challenges.
* `append()` on an erasure coded file will throw `IOException`.
* `append()` and `truncate()` on an erasure coded file will throw `IOException`.
* `concat()` will throw `IOException` if files are mixed with different erasure
coding policies or with replicated files.
* `setReplication()` is no-op on erasure coded files.
* `hflush()` and `hsync()` on `DFSStripedOutputStream` are no-op. Thus calling
`hflush()` or `hsync()` on an erasure coded file can not guarantee data
being persistent.