You are currently on IBM Systems Media’s archival website. Click here to view our new website.

Server Outage Classifications


Information Technology Intelligence Corp. defines Tier 1, Tier 2 and Tier 3 server outages as follows:

Tier 1: These are the typically minor, common, albeit annoying occurrences. Network administrators can usually resolve such incidents in fewer than 30 minutes for dependent users. Tier 1 incidents can usually be resolved by rebooting the server (locally and remotely) and rarely involve data loss. Tier 1 outages range from something as innocuous as accidentally unplugging the server to applying a quick update.

Tier 2: These are moderate issues in which the server may be offline from one hour to four hours. Tier 2 problems may require the intervention of more than one network administratorto troubleshoot. It frequently disrupts network operations for the company’s end users and possibly business partners, customers and suppliers attempting to access data on an affected corporate extranet. Data loss is possible, and some remediation is required.

Tier 3: This is the most severe incident. Tier 3 outages are longer than four hours in terms of service unavailability, the corporation’s associated dependent users and the remediation efforts of IT. Tier 3 outages almost always require multiple network administrators to resolve issues, and there is a greater probability of data loss or damage to systems. Another real threat associated with a protracted Tier 3 outage is potential lost business and damage to the company’s reputation. Tier 3 outages can also be man-made—such as a backhoe cutting a power line or a prolonged power outage—or be triggered when a natural disaster, such as a hurricane, flood or tornado occurs. Other causes of Tier 3 outages include an external security breach/hack, if the IT department cannot obtain the necessary technical support from its vendors or if no fix is available for an otherwise a minor issue.