Ceph releases
Each release of Ceph has a numeric version. Major releases also receive cephalopod code-names in alphabetical order. Through the Luminous release the Ceph community tagged a new major version about twice a year, alternating between Long Term Support (LTS) and stable releases. The latest two LTS releases were officially supported, but only the single latest stable release.
The release numbering scheme has changed since the first edition of Learning Ceph was published. Earlier major releases were tagged initially with a version number (0.87) and were followed by multiple point releases (0.87.1, 0.87.2, ...). Releases beginning with Infernalis however are numbered as shown:
The major release number matches the letter of the alphabet of its code name (for example I is the ninth letter of the English alphabet, so 9.2.1 was named Infernalis). As we write, there have been four releases following this numbering convention: Infernalis, Jewel, Kraken, and Luminous.
The early versions of each major release have a type of 0 in the second field, which indicates active pre-release development status for early testers and the brave of heart. Later release candidates have a type of 1 and are targeted at test clusters and brave users. A type of 2 represents a general-availability, production-ready release. Point releases mostly contain security and bug fixes, but sometimes offer functionality improvements as well.
https://github.com/ceph/ceph/pull/18117/files