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https://issues.apache.org/jira/browse/HDFS-7129?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14152239#comment-14152239
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Xiaoyu Yao commented on HDFS-7129:
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Thanks [~cnauroth] for the review.
Good catch on 1! Yes, the intension is to use {code}Time#monotonicNow {code}
throughout the class.
Agree on 2 and will update the patch to fail the test if initJMX() fails.
> 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
>
>
> 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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