Le jeu. 22 août 2019 à 16:47, Mark Phippard <firstname.lastname@example.org> a écrit :
>> Cannot they become obsolete when a new version of SVN comes
> No. It is a valid copy of the repository.
>> Are they portable across operating systems and
>> filesystems? (I fear not)
> Yes, they are absolutely portable across OS and FS. As is the repos itself.
This prove to work in practice, but is it guaranteed that the fsfs
repos format remain compatible between 1.X subsequent subversion
Yes it is.
When you upgrade your server to new version you do not have to touch existing repositories. Think what a nightmare that would be for hosting services or anyone with a lot of repositories. It is not uncommon for a new release to introduce a new repository format with some new features ... though usually it is just some new efficiency in how the data is stored. You need to dump/load if you are interested in getting these changes but the server is capable of reading and writing every repository format.
It appears the fsfs repos format sometime change between 1.X
subversion releases. For example, Subversion 1.9 introduced fsfs
format version 7. The release notes  mention and recommend to do a
full dump / load cycle to be able to take benefits of this new format
Correct, you need to dump/load if you want to use the new format.
There is nothing wrong with having full dumps of your repository and you need it to upgrade the format, but hot-copies are totally viable as a backup and have a lot of advantages when it comes to the recovery process in the event you need the backup. I would not rush to using new formats just because they are available. I have avoided the new format in 1.9 as its benefits seemed tuned to scenarios that do not match my needs at all and it has slower performance for what I think is the most common use case which is using the Apache server hosting lots of repositories.
Anyway ... the only danger of a repository format is if you upgrade to latest and then for some reason need to downgrade your server binaries to an older version. You can always use an older format with a newer version.