Robert Coli created CASSANDRA-5850:
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Summary: change gc_grace_seconds default to 28 days
Key: CASSANDRA-5850
URL: https://issues.apache.org/jira/browse/CASSANDRA-5850
Project: Cassandra
Issue Type: Improvement
Components: Core
Affects Versions: 2.0 beta 2
Reporter: Robert Coli
Priority: Trivial
Current default for gc_grace_seconds is 10 days. Attached patch changes all
instances of this 10 day default to 28 days.
Rationale :
- 10 days is arbitrary, there is nothing special about the current value
- human societies do not operate on cycles which are a multiple of 10 days,
they operate on a cycle of 7 day weeks
- operators must run repair once every gc_grace_seconds, and with typical data
sizes (and compaction/streaming throttling) this might run for a significant
fraction of 10 days
- repair often fails, and detecting and working around that failure might also
take a significant fraction of 10 days
- repair is the heaviest operation one can run on a cassandra cluster and
operators are therefore motivated to run it ~3x less frequently by default
- the worst case impact is keeping data around for 18 days longer than the
previous default, and this only occurs in CFs which actually take DELETE
operation
- 28 days is an even multiple of 7 days and easily comprehensible as a default
time in which to schedule repair
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