Re1: My hosting provider, for its VPS plans, offers what they call “slices”, each slice adds “processor cores, memory and storage”. Currently it doesn’t seem possible to add storage without adding CPU cores and RAM at the same time. There are plans for SSD and HDD though, so you can choose between speed or capacity as per your needs. In this particular case, /home is 2TB.
Re2: Unfortunately, the “domains” folder (as in /home/userid/domains/domain.com/public_html) is imposed by DirectAdmin. In reality I'm hosting moodle in /home/userid/moodle/ with subfolders for web (code), moodledata, cron (logs) and moodlebackup (course backups), where the "web" subfolder is symlink'd to /home/userid/domains/domain.com/public_html. If multiple instances of Moodle are deployed to same server (different domain or subdomain), one level is added to the folder hierarchy, but still all Moodle related data is within one folder (found it easier to admin this way).
Re2: Unfortunately, the “domains” folder (as in /home/userid/domains/domain.com/public_html) is imposed by DirectAdmin. In reality I'm hosting moodle in /home/userid/moodle/ with subfolders for web (code), moodledata, cron (logs) and moodlebackup (course backups), where the "web" subfolder is symlink'd to /home/userid/domains/domain.com/public_html. If multiple instances of Moodle are deployed to same server (different domain or subdomain), one level is added to the folder hierarchy, but still all Moodle related data is within one folder (found it easier to admin this way).
I consider the issue for sessions of moodledata now resolved. Added my final solution to the main thread...