I'd prefer to see the default go from STCS to UCS, probably with scaling_parameters T4. That's essentially the same as STCS but without the ridiculous SSTable growth, allowing us to leverage the fast streaming path more often. I don't think there's any valid use cases for STCS anymore now that we have UCS.
That said, many have taken issue with the state of UCS docs, myself included, so that would need to be addressed with any default change. I don't think we should mark TWCS as experimental. Maybe we prevent repairs to tables using TWCS, or do a better job of encouraging folks to use incremental repair at higher frequencies. It's definitely not experimental though. Side note: I think experimental has been over-used and has lost all meaning. How is Java 17 experimental? Very confusing for the community. I think TWCS should use UCS under the hood which would address streaming performance (and thus node density) or UCS could be updated to allow for time window's options. Either would solve issue #3 in your list. Jon On Fri, Dec 6, 2024 at 5:36 PM Paulo Motta <pa...@apache.org> wrote: > Hi, > > It’s 2024 and users are still facing issues due to misconfigured > compaction when using default configuration. > > I would like to start a conversation around improving compaction defaults > in 5.1/trunk, so users trying out CQL transactions don’t need to worry > about tuning compaction. > > A few suggestions: > > 1) Make LeveledCompactionStrategy default on cassandra.yaml, UCS default > on cassandra_latest.yaml ? > > 2) Does TWCS work out of the box with repairs and hints? My understanding > is that due to CASSANDRA-10496 this causes droppable tombstone issues when > in combination with repair and hints (see more on this thread [1]). We > should either fix this or mark TWCS experimental. > > 3) When STCS is used with deletions/TTL, tombstones accumulate in higher > level stables when unchecked_tombstone_compaction is disabled (see > CASSANDRA-6563). I propose having adding a new setting “auto” enabled by > default that will have this set to true when STCS/TWCS is used. > > I believe addressing these points will improve user experience with > Cassandra. > > I apologize in advance if these topics were discussed in recent threads. I > would be happy to get pointers of related discussions on this topic. > > I will be happy to create JIRA if there’s agreement on addressing these > items. > > Thanks, > > Paulo > > [1] - > > https://user.cassandra.apache.narkive.com/VQOacfnT/twcs-repair-create-new-buckets-with-old-data >
