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https://issues.apache.org/jira/browse/CASSANDRA-14647?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16583121#comment-16583121
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Dinesh Joshi commented on CASSANDRA-14647:
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Hey Vitali, thanks for the report. [~krummas] any idea what is going on here?
Would changing compaction strategies cause this issue?
> Reading cardinality from Statistics.db failed
> ---------------------------------------------
>
> Key: CASSANDRA-14647
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14647
> Project: Cassandra
> Issue Type: Bug
> Components: Compaction
> Environment: Clients are doing only writes with Local One, cluster
> consist of 3 regions with RF3.
> Storage is configured wth jbod/XFS on 10 x 1Tb disks
> IOPS limit for each disk 500 (total 5000 iops)
> Bandwith for each disk 60mb/s (600 total)
> OS is Debian linux.
> Reporter: Vitali Djatsuk
> Priority: Major
> Fix For: 3.0.x
>
> Attachments: cassandra_compaction_pending_tasks_7days.png
>
>
> There is some issue with sstable metadata which is visible in system.log, the
> messages says:
> {noformat}
> WARN [Thread-6] 2018-07-25 07:12:47,928 SSTableReader.java:249 - Reading
> cardinality from Statistics.db failed for
> /opt/data/disk5/data/keyspace/table/mc-big-Data.db.{noformat}
> Although there is no such file.
> The message has appeared after i've changed the compaction strategy from
> SizeTiered to Leveled. Compaction strategy has been changed region by region
> (total 3 regions) and it has coincided with the double client write traffic
> increase.
> I have tried to run nodetool scrub to rebuilt the sstable, but that does not
> fix the issue.
> So very hard to define the steps to reproduce, probably it will be:
> # run stress tool with write traffic
> # under load change compaction strategy from SireTiered to Leveled for the
> bunch of hosts
> # add more write traffic
> Reading the code it is said that if this metadata is broken, then "estimating
> the keys will be done using index summary".
>
> [https://github.com/apache/cassandra/blob/cassandra-3.0.17/src/java/org/apache/cassandra/io/sstable/format/SSTableReader.java#L247]
>
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