LiuGuH commented on code in PR #6926:
URL: https://github.com/apache/hadoop/pull/6926#discussion_r1887840665
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hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/fsdataset/impl/BlockPoolSlice.java:
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@@ -1152,4 +1153,14 @@ void setDeleteDuplicateReplicasForTests(
this.deleteDuplicateReplicas = deleteDuplicateReplicasForTests;
}
+ public File hardLinkOneBlock(File src, File srcMeta, Block dstBlock) throws
IOException {
+ File dstMeta = new File(tmpDir,
+ DatanodeUtil.getMetaName(dstBlock.getBlockName(),
dstBlock.getGenerationStamp()));
+ HardLink.createHardLink(srcMeta, dstMeta);
+
+ File dstBlockFile = new File(tmpDir, dstBlock.getBlockName());
+ HardLink.createHardLink(src, dstBlockFile);
Review Comment:
>>do you use this feature on a large scale? Does creating a lot of hard
links have a maintenance impact on the system?
Now Hadoop version upgrade depends on linux hardlink. And hardlink is
lightweight and it only link a new pointer points to the original file.
>> Have you considered implementing it based on rename?
Now src and dst have different block name. And they point the same file
address. This is what hardlink works. @tomscut
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