SLATools.com provides a range of tools for better understanding and tracking your service SLA. These tools include an SLA Uptime Calculator, an Incident & SLA Breach Calculator and SLA Credit Calculator.
What is uptime? Uptime is the amount of time that a service is available and operational. This is generally the most important metric for a website, online service or web based provider.
The counterpart is downtime - the amount of time that a service is unavailable.
Uptime is commonly expressed as a percentage such as ‘99.9%’ over a given time period (generally month). For example a 99.9% uptime equates to 43 minutes and 50 seconds of downtime.
A Service Level Agreement (SLA) is document detailing the expected level of service guaranteed by a supplier or product. This document generally lays out metrics such as uptime expectations and any renumeration if these levels are not achieved.
Commonly people simplify the definition of SLA to simply refer to the specific uptime expectation of the product, for example, if a provider advertises a 99.9% uptime, and exceeds 43 minutes and 50 seconds of downtime, technically the SLA has been breached and the customer may be entitled to renumeration of some kind based on the agreement.
A service or hosting credit is a common way of providers reimbursing customers for a breach to an uptime percentage guaranteed in an SLA. This is at the terms of the provider, but generally follows a model of a sliding scale, such as ‘5% of the monthly cost per hour outside of SLA’.