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https://issues.apache.org/jira/browse/HDFS-7129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14152913#comment-14152913
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Arpit Agarwal commented on HDFS-7129:
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+1 for the patch. I will commit it shortly.
Two nitpicks we can clean up later:
# {{if (replicaInfo.getIsPersisted() == false)}} can just be written as {{if
(!replicaInfo.getIsPersisted()}}.
# We can eliminate {{FsDatasetImpl.discardRamDiskReplica}} since it just
forwards to {{ramDiskReplicaTracker.discardReplica}}.
> Metrics to track usage of memory for writes
> -------------------------------------------
>
> Key: HDFS-7129
> URL: https://issues.apache.org/jira/browse/HDFS-7129
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode
> Affects Versions: HDFS-6581
> Reporter: Arpit Agarwal
> Assignee: Xiaoyu Yao
> Attachments: HDFS-7129.0.patch, HDFS-7129.1.patch, HDFS-7129.2.patch,
> HDFS-7129.3.patch
>
>
> A few metrics to evaluate feature usage and suggest improvements. Thanks to
> [~sureshms] for some of these suggestions.
> # Number of times a block in memory was read (before being ejected)
> # Average block size for data written to memory tier
> # Time the block was in memory before being ejected
> # Number of blocks written to memory
> # Number of memory writes requested but not satisfied (failed-over to disk)
> # Number of blocks evicted without ever being read from memory
> # Average delay between memory write and disk write (window where a node
> restart could cause data loss).
> # Replicas written to disk by lazy writer
> # Bytes written to disk by lazy writer
> # Replicas deleted by application before being persisted to disk
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