Choosing the service it is important to know what kind of quality the service has. SLA (Service Level Agreement) is an agreement between the user and the service provider which fixes the quality of service parameters. For example, Internet service providers, use an indicator of the SLA as download and upload speeds and service availability. Cloud service guaranteed SLA indicates the availability of the year.
Talking about the availability of the system, often referred to "the nines system". In nine-system it is counted how many number nine there are in a row.
| SLA % | Downtime in a year * | Downtime in a month** | Downtime in a week |
|---|---|---|---|
| 90% ("one nine") | 36.5 days | 72 hours | 16.8 hours |
| 95% | 18.25 days | 36 hours | 8.4 hours |
| 98% | 7.30 days | 14.4 hours | 3.36 hours |
| 99% ("two nines") | 3.65 days | 7.20 hours | 1.68 hours |
| 99.5% | 1.83 days | 3.60 hours | 50.4 minutes |
| 99.8% | 17.52 hours | 86.23 minutes | 20.16 minutes |
| 99.9% ("three nines") | 8.76 hours | 43.2 minutes | 10.1 minutes |
| 99.95% | 4.38 hours | 21.56 minutes | 5.04 minutes |
| 99,98% - Termnet | 1.75 hours | 8.64 minutes | 2.01 minutes |
* 1 year = 365 days
** 1 month = 30 days
To provide the service with defined quality a service level agreement will be contracted which documents the quality of service parameters. The customer can monitor the parameters either by himself or by monitoring server logs compiled on the basis of periodic summaries.
Quality of vInfra machines service
The quality of service of 99.98 % cannot be guaranteed without a reliable infrastructure. To ensure quality service, we take the following actions:
- Virtualization – virtual server will be made independent of the physical server.
- Duplication of servers – while maintaining a physical server the virtual server will be copied into another virtual machine without cancelling work.
- Enterprise-class disk systems - provide the speed and reliability.
- Duplicated network devices and connections - connections do not depend on a single device or connection.
- Duplicated physical infrastructure, power, UPS, generators and cooling.
- Quality control - constant monitoring and fault notification.