DigitalOcean (DO) has super cheap yet powerful hosting plans. Starting with the most basic $5 plan I have been able to 'get started' with setting up WP Multisite as a working set up.
I need to figure out now, rather than later what kind of disk space requirements will be sufficient for hosting up to 500 sites and beyond.
DO's 'fast resizing' between server packages does not include disk space whereby a 'snapshot' must be taken first then restored to a new droplet with a new IP. This will of course cause issues with sites that are already domain mapped to the old droplet's IP which will need to be reassigned.
The next level of DO's hosting with regard disk space is 30GB, 40GB, 60GB, 80GB and higher.
In the spirit of "pay as we grow" I wanted to keep costs down so the questions are: 1) is it really a big deal to migrate to a better host package later and inform clients their site's IP needs to change? 2) how can I calculate and estimate a reasonable number of sites an amount of disk space will hold?