linux system admin - 3 Linux servers monthly work

We looking for a system admin to manage and maintain 3 dedicated servers. The servers are used to host websites, with a decent traffic, big database. It's critical NOT to have down time and to back up files and data base often (done with remote backup). Systems: - CentOS - Ubuntu Skills: - general linux administration. - database administration of MySQL. - web application installation, configuration and management. - web security - general web development would be good. Tasks: - Update server - make sure the servers and web application are running fast - monitoring the servers - regular clean up of the servers - management of backups (database + files.) - security We are looking for someone to work for us for a long time on a monthly basis, our budget is $100/month. Please tell us about your experience. Thanks, Søren