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Tsz Wo Nicholas Sze commented on HDFS-9079: ------------------------------------------- Thanks for the explanation. Is this an incompatible change? > Erasure coding: preallocate multiple generation stamps and serialize updates > from data streamers > ------------------------------------------------------------------------------------------------ > > Key: HDFS-9079 > URL: https://issues.apache.org/jira/browse/HDFS-9079 > Project: Hadoop HDFS > Issue Type: Sub-task > Components: erasure-coding > Affects Versions: HDFS-7285 > Reporter: Zhe Zhang > Assignee: Zhe Zhang > Attachments: HDFS-9079-HDFS-7285.00.patch, HDFS-9079.01.patch, > HDFS-9079.02.patch, HDFS-9079.03.patch, HDFS-9079.04.patch, HDFS-9079.05.patch > > > 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. -- This message was sent by Atlassian JIRA (v6.3.4#6332)