Rick Branson created CASSANDRA-7764:
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Summary: RFC: Range movements will "wake up" previously invisible
data
Key: CASSANDRA-7764
URL: https://issues.apache.org/jira/browse/CASSANDRA-7764
Project: Cassandra
Issue Type: Bug
Reporter: Rick Branson
Presumably this has been going on as long as Cassandra has existed, but wanted
to capture it here since it came up in an IRC discussion. This issue will
probably show up on any cluster eventually.
Scenario:
1) Start with a 3-node cluster, RF=1
2) A 4th node is added to the cluster
3) Data is deleted on ranges belonging to 4th node
4) Wait for GC to clean up some tombstones on 4th node
4) 4th node removed from cluster
5) Deleted data will reappear since it was dormant on the original 3 nodes
This could definitely happen in many other situations where dormant data could
exist such as inconsistencies that aren't resolved before range movement, but
the case above seemed the most reasonable to propose as a real-world problem.
The cleanup operation can be used to get rid of the dormant data, but from my
experience people don't run cleanup unless they're low on disk. It's definitely
not a best practice for data integrity.
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