Some data that I believe is relevant here. Numerically it's safe to assume there's over 10,000 ASF C* clusters out in the world (5,500 in China alone). In surveys (both informal polling and primary research), at least 1/3rd of folks are running the 3.X latest if I recall correctly.
Basic conclusions we can draw from these data points: 1) There are thousands of clusters running some form of post 3.0, so we can expect it to be *stable enough to upgrade through* 2) We have to support at least 3.11 → 4.0 If 1/3rd of our users are running 2.1, 1/3rd 3.0, and 1/3rd 3.11 (hand-waving, probably more in the 25 vs. 40 etc but splitting hairs), there's clearly a significant value-add in usability of skipping majors (3.0->4.0). Depending on how we define "done" and "supported" for upgrade testing, this will represent a significant development burden. >From a *functional MVP* perspective on what upgrade paths we need to support, the absolute minimum would be 2.1 → 3.0 → 3.11 → 4.0 If anyone wants to step in and officially support the 3.0 → 4.0 line, that's fantastic both for the project community and for users. But as far as basic table stakes, I can't think of a logical reason 3.0 → 4.0 as an upgraded path should be considered a blocker for releasing 4.0 GA. On Fri, Oct 09, 2020 at 9:53 AM, Mick Semb Wever <m...@apache.org> wrote: > At The Last Pickle we have always recommended avoiding 3.0, including > upgrading from 2.2 directly to 3.11. > We (now DataStax) will continue to recommend that folk upgrade to the > latest 3.11 before upgrading to 4.0. > > To clarify that^, if it wasn't obvious, I wasn't making a statement about > DataStax at at large, but about those of us at TLP and now the team > providing the consulting for Apache Cassandra from DataStax. >
