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ASF GitHub Bot commented on HDFS-17463: --------------------------------------- hiwangzhihui commented on PR #6736: URL: https://github.com/apache/hadoop/pull/6736#issuecomment-2106760458 @Hexiaoqiao I agree with your propose , We will proceed with work for it. Thank you for your guide. > Support the switch StringTable Split ID feature > ----------------------------------------------- > > Key: HDFS-17463 > URL: https://issues.apache.org/jira/browse/HDFS-17463 > Project: Hadoop HDFS > Issue Type: Improvement > Components: namenode > Affects Versions: 3.2.0, 3.3.5, 3.3.3, 3.3.4 > Reporter: wangzhihui > Priority: Major > Labels: pull-request-available > Attachments: Image_struct.png, error.png > > > desc: > * > Hadoop 3.2 introduced optimization features for HDFS StringTable > (b60ca37914b22550e3630fa02742d40697decb3), It resulted in lower versions of > Hadoop upgraded to 3.2 and later versions not supporting downgrade > operations. > !error.png! > * This issue has also been discussed in HDFS-14831, and it is recommended to > revert the feature, but it cannot fundamentally solve the problem。 > * > Therefore, we have added an optimization to support downgrading > > Solution: > * First, we will add the "dfs. image. save. splitId. stringTable" conf > switch "StringTable optimization feature" is enabled > * When the conf value is false, an Image file compatible with lower versions > of HDFS is generated to support downgrading. > * > The difference in HDFS Image file format between Hadoop 3.1.1 and Hadoop 3.2 > is shown in the following figure. > * With the sub-sections feature introduced in HDFS-14617, Protobuf can > support compatible reading. > * > The data structure causing incompatible differences is mainly StringTable. > !Image_struct.png|width=396,height=163! > * In "dfs.image.save.splitId.stringTable = false " the Id generation order > of StringTable starts from 0 to Integer.Max. When true, the Id value range > follows the latest rules. > -- This message was sent by Atlassian Jira (v8.20.10#820010) --------------------------------------------------------------------- To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org