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https://issues.apache.org/jira/browse/HDFS-16949?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17700357#comment-17700357
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ASF GitHub Bot commented on HDFS-16949:
---------------------------------------
rdingankar opened a new pull request, #5479:
URL: https://github.com/apache/hadoop/pull/5479
…e percentile metrics
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### Description of PR
PR #5397 added ReadTransferRate quantiles to calculate the rate which data
is read per unit of time.
With percentiles the values are sorted in ascending order and hence for the
transfer rate p90 gives us the value where 90 percent rates are lower (worse),
p99 gives us the value where 99 percent values are lower (worse).
Note that value(p90) < p(99) thus p99 is a better transfer rate as compared
to p90.
However as the percentile increases the value should become worse in order
to know how good our system is.
Hence instead of calculating the data read transfer rate, we should
calculate it's inverse. We will instead calculate the time taken for a GB of
data to be read. ( seconds / GB )
After this the p90 value will give us 90 percentage of total values where
the time taken is less than value(p90), similarly for p99 and others.
Also p(90) < p(99) and here p(99) will become a worse value (taking more
time each byte) as compared to p(90)
### How was this patch tested?
Updated Unit Tests.
### For code changes:
- [Y ] Does the title or this PR starts with the corresponding JIRA issue id
(e.g. 'HADOOP-17799. Your PR title ...')?
- [ NA ] Object storage: have the integration tests been executed and the
endpoint declared according to the connector-specific documentation?
- [ NA ] If adding new dependencies to the code, are these dependencies
licensed in a way that is compatible for inclusion under [ASF
2.0](http://www.apache.org/legal/resolved.html#category-a)?
- [ NA ] If applicable, have you updated the `LICENSE`, `LICENSE-binary`,
`NOTICE-binary` files?
> Update ReadTransferRate to ReadLatencyPerGB for effective percentile metrics
> ----------------------------------------------------------------------------
>
> Key: HDFS-16949
> URL: https://issues.apache.org/jira/browse/HDFS-16949
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: datanode
> Reporter: Ravindra Dingankar
> Assignee: Ravindra Dingankar
> Priority: Minor
> Fix For: 3.3.0, 3.4.0
>
>
> HDFS-16917 added ReadTransferRate quantiles to calculate the rate which data
> is read per unit of time.
> With percentiles the values are sorted in ascending order and hence for the
> transfer rate p90 gives us the value where 90 percent rates are lower
> (worse), p99 gives us the value where 99 percent values are lower (worse).
> Note that value(p90) < p(99) thus p99 is a better transfer rate as compared
> to p90.
> However as the percentile increases the value should become worse in order to
> know how good our system is.
> Hence instead of calculating the data read transfer rate, we should calculate
> it's inverse. We will instead calculate the time taken for a GB of data to be
> read. ( seconds / GB )
> After this the p90 value will give us 90 percentage of total values where the
> time taken is less than value(p90), similarly for p99 and others.
> Also p(90) < p(99) and here p(99) will become a worse value (taking more time
> each byte) as compared to p(90)
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