Zhe Zhang created HDFS-9079:
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Summary: Erasure coding: preallocate multiple generation stamps
when creating striped blocks
Key: HDFS-9079
URL: https://issues.apache.org/jira/browse/HDFS-9079
Project: Hadoop HDFS
Issue Type: Sub-task
Reporter: Zhe Zhang
A non-striped DataStreamer goes through the following steps in error handling:
{code}
1) Finds error => 2) Asks NN for new GS => 3) Gets new GS from NN => 4) Applies
new GS to DN (createBlockOutputStream) => 5) Ack from DN => 6) Updates block on
NN
{code}
To simplify the above we can preallocate GS when NN creates a new striped block
group ({{FSN#createNewBlock}}). For each new striped block group we can reserve
{{NUM_PARITY_BLOCKS}} GS's. Then steps 1~3 in the above sequence can be saved.
If more than {{NUM_PARITY_BLOCKS}} errors have happened we shouldn't try to
further recover anyway.
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