I want to offer a free remote server monitoring service for few clients, it will be a basic monitoring solution including few windows services, free HDD space,etc. It would be nice for the software to send alerts and automated (customized) reports once a week showing up time, problems and other information. Another nice option to have would be a possibility of a client to log in via a web portal to check logs, and stats, one client should be able to see only his or her servers.
What would be the best software for this task? It will run on VMware ESXi behind a firewall, it could be either Windows or Linux based. Since I am going to offer this service for free a free software would be nice, I am also willing to pay some $$$ for it to get better functionality. Ease of deployment/installation would help a lot.
Appreciate any suggestions.