Service level agreements in Cloud computing
A Service Level Agreement (SLA) is a performance assurance document negotiated between a cloud services provider and the client. Historically, all SLAs in cloud computing were individually negotiated between the provider and consumer. However, with the emergence of large-scale, utility-based cloud service providers, most SLAs are now standardized unless the client is a significant consumer of the service.
SLAs can be categorized into the following types:
- Customer-Based SLA
- Service-Based SLA
- Multilevel SLA
Parameters Typically Defined in SLAs
SLAs often specify the following key parameters:
- Service availability or uptime
- Response time (latency)
- Reliability of service components
- Accountability of each party
- Warranties
If the service provider fails to meet the specified minimum performance standards, penalties are incurred as per the SLA. In essence, SLAs act like insurance policies, requiring the service provider to compensate the consumer in case of any lapses.
Examples of SLAs in Practice
1. Microsoft Azure SLA for Compute and Storage
- Compute SLA guarantees external connectivity for a client’s internet-facing roles at least 99.95% of the time, provided two or more role instances are deployed across separate fault and upgrade domains. Additionally, all role instances are monitored, with a 99.9% guarantee of detecting when a role instance fails to start or operate properly.
- Example Output: Ensures consistent uptime for applications hosted on Azure virtual machines, even during routine maintenance or unexpected outages.
2. Microsoft SQL Azure SLA
- Guarantees 99.9% monthly availability for database connectivity between SQL Azure and its internet gateway. The “Monthly Availability” ratio is calculated by comparing the time the database was available to the total time in the month, measured in intervals. Availability compensation is offered for any full month with connectivity issues.
- Example Output: Reliable access for an e-commerce database system handling transactions and customer data.
SLA Lifecycle Steps
1. Discover Service Provider
- Identify a service provider capable of meeting organizational needs through research, proposals, or vendor engagement.
2. Define SLA
- Outline and agree on service requirements, including performance objectives, metrics, and targets.
3. Establish Agreement
- Formalize terms and conditions, including SLA details, penalties for non-compliance, and monitoring processes.
4. Monitor SLA Violations
- Regularly track service performance to ensure compliance. Report and address any identified violations promptly.
5. Terminate SLA
- If the provider consistently fails to meet performance standards or if the client is dissatisfied, the SLA may be terminated either mutually or through enforcement of penalties.
6. Enforce Penalties for SLA Violations
- Impose penalties for non-compliance, such as financial compensation or reduced service levels.
Advantages of SLAs
1. Improved Communication
- Establishes a clear framework for communication, ensuring mutual understanding of service expectations.
2. Increased Accountability
- Holds providers responsible for meeting agreed-upon standards while giving clients the ability to track performance
3. Alignment with Business Goals
- Ensures that the delivered services align with the client’s objectives through well-defined performance goals.
4. Reduced Downtime
- Minimizes service disruptions by defining clear protocols for issue resolution.
5. Cost Management
- Provides tools to monitor service levels and manage costs effectively, ensuring optimal value for money.
Disadvantages of SLAs
1. Complexity
Developing and managing SLAs can be resource-intensive and require considerable effort.
2. Rigidity
- SLAs may lack the flexibility needed to adapt to changing business needs.
3. Limited Service Options
- Customers might be restricted to predefined service offerings in the SLA.