Читать книгу The Official (ISC)2 SSCP CBK Reference - Mike Wills - Страница 117

To be effective (and enforceable), an SLA must use clear and unambiguous language to specify its terms and conditions for all services that each party brings to the contract. Key performance indicators or other quality of service metrics should also be defined in the SLA, along with explanations as to how they are measured, computed, and reported. Without this, there is no basis for measuring or knowing whether a provider is providing the agreed level of service.

Amazon Web Services (AWS), a well-known cloud service provider, uses a standard SLA for their Elastic Cloud Compute (EC2) services, which you can review at https://aws.amazon.com/ec2/sla/. Among other items, it specifies a server uptime metric:

 If your servers enjoy anything above 99.99 percent uptime, AWS has met its SLA.

 If your servers have anywhere between 99.00 and 99.99 percent uptime for the month, you will get a 10 percent discount on the service fee for that period.

 For anything less than 99.00 percent, you will get a 30 percent discount for your hosting for that month.

This is a good example not only because the metrics and terms are clear but also because it is clear about what happens in the event of noncompliance with the SLA. The contracting manager (in conjunction with the organization's IT department) must determine whether the price reduction would realistically offset the loss in productivity a service outage would cause; if the cost of the outage outweighs the benefit of the rebate/discount, the SLA is insufficient for the customer's needs.