We run the demo and admin together in 512 of RAM and < 1 Gig of disk space. This may be ok for small sites, but we'd recommend the minimum of 1 GIG of RAM and 5GB disk.
The sizing of a Broadleaf Commerce installation can vary quiet a bit depending on usage. Some thought should be put into a production setup. I'll provide some simple guidelines below but understand that it is difficult to provide a formula for sizing an eCommerce site due to the variety of integrations, product catalogs, and other factors that are unique to each business.
Considerations for disk size include:
1. The number and size of your static assets (JS, images, videos, etc.)
2. The amount of logging that you will use
For RAM, most sites will run optimally with 1GB - 2GB of RAM per VM. The major decision factors on sizing the RAM are the size of your product catalog and content items that you want to cache. Even large catalogs will do fine in the RAM proposed above and we don't recommend upping beyond the 2GB threshold.
The number of instances of Broadleaf that you should run depends upon a number of factors. As with any framework, a key function of the application architect is to properly size and scale the application.
1. For reliability, you may want to build an N+1 architecture. If your site needs 1 server to operate under peak load, you actually install 2 so that if one goes down things remain normal.
2. Determining the required number of servers under peak load requires load testing and will be highly dependent on how you've customized the application. Utilizing the out-of-box caching strategies and efficient programming practices, a single server should be able to process thousands of orders per day and service tens of thousands of requests. Additional tuning can increase these baselines. Additional integrations and heavy database access can negatively impact scalability and performance under volume.
We've taken efforts to make sure that Broadeaf Commerce will scale as well as or better than any other eCommerce platform.
Hope this helps,