IT service management

ITIL & service management

ITIL is a best-practice framework for delivering IT as a *service* aligned to business needs, rather than as a pile of technology.

SLA

A Service Level Agreement is a contract setting measurable targets — typically availability (uptime %), plus response and resolution times.

Incident vs problem

• Incident: an unplanned interruption to a service — the goal is to *restore service fast*, even with a temporary workaround.
• Problem: the underlying root cause of one or more incidents — the goal is to *fix it permanently*.

Availability

Availability = MTBF / (MTBF + MTTR) — mean time between failures over the whole period. A longer MTBF and a shorter repair time (MTTR) both push availability toward 100%.