We have platform project running for one of our customers using a singular code base that is deployed onto separate database instances, one per site (total of 15). This is undesirable for many reasons, and we are now looking into how one might merge these different instances into a single multi-site instance, with a single database.
My first instinct was to, on a new database, set up each site as you would normally. Then for each existing database import the respective site tree into the appropriate site using import/export data in the admin view.
Please share any thoughts or experiences you have.
Thanks in advance!
I haven't done anything similar, but I don't see any problems with what you describe. Not sure what will happen if you have global assets with the same path and name, though.
Access rights per subtree works fine.
I haven't migrated existing content, as you are planning to do, but I have worked with multi-site solutions. I see no issues with how you are planning to set it up.
Each site can have it's own "For this site"-folder for media/blocks (checkbox when you create the new site in admin mode). There will also be a "For all sites"-folder. Not sure where the media/blocks will end up when you import from a single site solution.