The SME Server is designed to run without intervention 24 hours per day, seven days a week. This reliability has been designed from the ground up: stable, well supported versions of the Linux kernel and applications, RAID disk mirroring, automatic firewall, and process supervision. Where applications have been shown to be insecure or unreliable, we use stable, secure replacements. The modular architecture allows this to be done without affecting the system administrator's view of the system and with only localised effect on the developer's view.