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https://issues.apache.org/jira/browse/HDFS-17936?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18090266#comment-18090266
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ASF GitHub Bot commented on HDFS-17936:
---------------------------------------
lfxy opened a new pull request, #8558:
URL: https://github.com/apache/hadoop/pull/8558
The current slow disk detection does not differentiate between storage
types. When a DataNode has 1 SSD and 10 HDDs with
dfs.datanode.max.slowdisks.to.exclude=2 and
dfs.datanode.min.outlier.detection.disks=5, if the SSD is under heavy
read/write load, the single SSD may be identified as a slow disk. Client tasks
writing SSD data to that DataNode will then fail to select a volume and report:
No more available volumes.
`public V chooseVolume(List<V> volumes, long replicaSize, String storageId)
throws IOException {
if (volumes.size() < 1) {
throw new DiskOutOfSpaceException("No more available volumes");
}
...
} `
Therefore, slow disk detection should be performed separately for each
storage type. If the number of disks of a given storage type is less than
dfs.datanode.min.outlier.detection.disks, detection for that storage type is
skipped entirely.
> Detect slow disks separately by storage type
> --------------------------------------------
>
> Key: HDFS-17936
> URL: https://issues.apache.org/jira/browse/HDFS-17936
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 3.6.0
> Reporter: caozhiqiang
> Assignee: caozhiqiang
> Priority: Major
>
> The current slow disk detection does not differentiate between storage types.
> When a DataNode has 1 SSD and 10 HDDs with
> dfs.datanode.max.slowdisks.to.exclude=2 and
> dfs.datanode.min.outlier.detection.disks=5, if the SSD is under heavy
> read/write load, the single SSD may be identified as a slow disk. Client
> tasks writing SSD data to that DataNode will then fail to select a volume and
> report: No more available volumes.
> {code:java}
> public V chooseVolume(List<V> volumes, long replicaSize, String storageId)
> throws IOException {
> if (volumes.size() < 1) {
> throw new DiskOutOfSpaceException("No more available volumes");
> }
> ...
> } {code}
> Therefore, slow disk detection should be performed separately for each
> storage type. If the number of disks of a given storage type is less than
> dfs.datanode.min.outlier.detection.disks, detection for that storage type is
> skipped entirely.
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