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https://issues.apache.org/jira/browse/HDFS-14313?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16865274#comment-16865274
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Lisheng Sun commented on HDFS-14313:
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[~jojochuang] Thanks for your review.
{quote}FsDatasetImpl#deepCopyReplica() needs to be synchronized on datasetLock.
Additionally I am not sure the impact of creating creating millions of
ReplicaInfo for dense DataNodes. That sounds quite heavy.
{quote}
I consider this point when developing the feature. And do test.
||Count(ReplicaInfo) of DataNode ||Time of synchronized on datasetLock||
|1039864|314ms|
|343866|89ms|
We get same result hundred milliseconds of millions ReplicaInfos in
production environment. The feature has been running for a long time for XiaoMi
HBase service and does not affect their performance. Thanks.
> Get hdfs used space from FsDatasetImpl#volumeMap#ReplicaInfo in memory
> instead of df/du
> ----------------------------------------------------------------------------------------
>
> Key: HDFS-14313
> URL: https://issues.apache.org/jira/browse/HDFS-14313
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode, performance
> Affects Versions: 2.6.0, 2.7.0, 2.8.0, 2.9.0, 3.0.0, 3.1.0
> Reporter: Lisheng Sun
> Assignee: Lisheng Sun
> Priority: Major
> Attachments: HDFS-14313.000.patch, HDFS-14313.001.patch
>
>
> There are two ways of DU/DF getting used space that are insufficient.
> # Running DU across lots of disks is very expensive and running all of the
> processes at the same time creates a noticeable IO spike.
> # Running DF is inaccurate when the disk sharing by multiple datanode or
> other servers.
> Getting hdfs used space from FsDatasetImpl#volumeMap#ReplicaInfos in memory
> is very small and accurate.
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