you know *nothing* about my infrastructure you know *nothing* about my load-balancers you know *nothing* about the vSpehre cluster
These are definitely true. All I know is that it's VMware :) But im interested. What do you do in that infrastructure when your roundcube load exceeds the capabilities of your vmware host server? Do you buy a larger vmware host server?
it does not happen because webmail is not a core-business here and *if it would* be relevant the shared session thing *would be* interesting but that is *not* a good reason to have it *default*
Thank you for clarifying, it all makes sense now.
The reason for this to be default is not because of shared sessions. It's because you need a database anyways, so having database sessions is basically 'free', and thus by far the easiest for almost all smaller roundcube installations. The roundcube code takes care of it all, and you dont have to worry about it. It just so happens that for larger installations where shared sessions are relevant this turns out to be useful as well.
The downside to that is that some installations, like yours, dont quite fit. You cant win them all. So, either code it or hire a coder and get it sorted if you really want this to work.
Cor