Sounds like what you really need to do is cleanup the current 3.11 first! Goal is to reduce size ... code is out of the question, but DB isn't. There are quite a few tables that are really 'trackers' and one could truncate them to re-coup overall size of a DB dump.
What are *all* the settings for time to retain data? Can tell ya there are too many to look at! :|
Bad idea not to migrate everything together ... DB, code, + minimal modledata/filedir/ - most of moodledata directories are cache related and should be purged upon migration - new server - new environment, etc.
One of the largest tables in a moodle could be mdl_logstore_standard_log ... the 'who done it' log.
If you are migrating to another server consider if you really need all that old who done it data. Could truncate that table and free up a bunch of DB space ... I bet. But, I really don't know ... cause it's your system and I've never seen it!
There are directories in your moodledata that could contain junk ... example: moodleata/temp/backup/
A production 4.5.6+ site
code - 1.4G
DB dump - 2.2G
177G moodledata/filedir
178G for all of moodledata
155 courses
7802 users
I don't do a tar ball backup of moodledata ... too large ... takes too long ... rather a progressive rsync to another directory on same server.
What's yours? you can give more exacting info via du -h source.
'SoS', Ken