>*Question #2*: Will the reduced DB still be compatible with my current >8.17 version in production? It would be great to have the downsized DB >for future migration. No. Citadel databases are never backward compatible. Once you start up thew new version of the server with the old database, it will perform upgrades on the database, making it incompatible with any previous version. We also set a configuration key indicating the newest version of Citadel Server that has written to the database, ensuring that no one accidentally attempts to open it with an older version. You *could* use database_cleanup.sh to recover disk space on an older server.
I'm not sure what your VM storage looks like, but on my VMs we use thin provisioned disks and set all of the filesystem options in the guest to return freed blocks back to the host system.
