I think there is a danger that when in comes to the next upgrade cycle there could be production clusters still running in CASSANDRA_4 mode, as the operators haven’t realised they need to move through the SCM levels. The default setting for a new cluster is CASSANDRA_4 and unless a new operator is going to use the new Cassandra 5 features they may not work out the SCM needs to change.
I can also imagine that there will be a lot left in UPGRADING mode, from what I can work out, for a cluster working within its performance boundaries there seems to be no real reason to go from UGRADING -> NONE, on very large clusters where a rolling restart is a pain, I currently don’t see a reason for recommending this last step, unless it is combined with something else that requires a rolling restart. SCM documentation has been hard to find, the only info I have found is in the NEWS.txt file, this also implies that SCM will be removed for the next release. Thanks Paul > On 11 Dec 2024, at 13:41, Sam Tunnicliffe <s...@beobal.com> wrote: > > My point is that the upgrade to 5.1/6.0 isn't really complete until the CMS > is initialised and this can't be done while running with SCM CASSANDRA_4 > because of the messaging service limitation. Until that point, schema changes > & node replacements are not supported which affects how long a bake time is > tolerable. > This specific issue could probably be fixed by revisiting the SCM > implementation in 5.1/6.0, so we should certainly do that but the fact > remains that we don't have great test coverage to indicate how clusters > behave when running in SCM for a prolonged period. > > Thanks, > Sam > >> On 11 Dec 2024, at 13:29, Brandon Williams <dri...@gmail.com> wrote: >> >> On Wed, Dec 11, 2024 at 7:22 AM Sam Tunnicliffe <s...@beobal.com> wrote: >>> >>> so running in any SCM mode for a prolonged period is not really viable. >> >> This is what many users want to do though, upgrade one DC and let it >> bake to see how it goes before continuing. I don't think that's >> unreasonable, but from working on CASSANDRA-20118 I know how difficult >> that is already. I don't think we've built enough SCM muscle yet to >> think about handling multiple previous versions. >> >> Kind Regards, >> Brandon >
