[jira] [Commented] (CASSANDRA-11420) Add the JMX metrics to track number of data flushed from memtable to disk

["Dikang Gu (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-11420?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15213744#comment-15213744 ] 

Dikang Gu commented on CASSANDRA-11420:
---------------------------------------

This is an interesting metrics, as we can use it to calculate the write amplification of C* node, using the formula:

wa = (compaction.BytesCompacted.Count) / (BytesFlushed.Count)

[~krummas] do you want to take a quick look?

> Add the JMX metrics to track number of data flushed from memtable to disk
> -------------------------------------------------------------------------
>
>                 Key: CASSANDRA-11420
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11420
>             Project: Cassandra
>          Issue Type: Improvement
>            Reporter: Dikang Gu
>            Assignee: Dikang Gu
>            Priority: Minor
>             Fix For: 3.x
>
>         Attachments: 0001-Add-the-metrics-of-how-many-bytes-we-flushed-from-me.patch
>
>
> 2016-03-24_02:30:38.39936 INFO  02:30:38 Completed flushing /data/cassandra/data/keyspace/column-family/column-family-tmp-ka-295782-Data.db (73.266MiB) for commitlog position ReplayPosition(segmentId=1458717183630, position=3690)
> It would be useful to expose the number of flushed bytes to JMX, so that we can monitor how many bytes are written by application and flushed to disk.



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