A service-level agreement (SLA) is a part of a service contract[disambiguation needed] where a service is formally defined. Particular aspects of the service – scope, quality, responsibilities – are agreed between the service provider and the service user. A common feature of an SLA is a contracted delivery time (of the service or performance).
As an example, Internet service providers and telcos will commonly include service level agreements within the terms of their contracts with customers to define the level(s) of service being sold in plain language terms. In this case the SLA will typically have a technical definition in terms of mean time between failures (MTBF), mean time to repair or mean time to recovery (MTTR); identifying which party is responsible for reporting faults or paying fees; responsibility for various data rates; throughput; jitter; or similar measurable details.
A cloud storage SLA is a service-level agreement between a cloud storage service provider and a customer that specifies details of the service, usually in quantifiable terms.
A typical cloud storage SLA articulates precise levels of service – such as, for example, 99.9% uptime – and the recourse or compensation that the user is entitled to should the provider fail to provide the service as described. Another normal cloud storage SLA detail is service availability, which specifies the maximum amount of time a read request can take, how many retries are allowed and so on.
The SLA should also define compensation for users if the specifications aren’t met. Cloud storage service providers usually offer a tiered service credit plan that gives users credits based on the discrepancy between SLA specifications and the actual service levels delivered.
Most public cloud storage services provide details of the service levels that users can expect on their websites and these will likely be the same for all users. However, an enterprise establishing service with a private cloud storage provider may be able to negotiate a more customized deal. In this case an SLA might include specifications for retention policies, the number of copies that will be retained, storage locations and so on.
It’s important to read an SLA closely and examine the ramifications. For example, 99.9% uptime, a common stipulation, translates to nine hours of outage per year. For some mission critical data, that may not be adequate. You should also check to see how terms are defined.
Microsoft Azure Storage Section
Service Level Agreement (SLA)
It is very important to review your SLA, Specially if you are running Servers which your customers depend their uptime. If you are reselling Storage and or Cloud services not only you as a customer of the Cloud Company get affected, but your customer will and that is when you will incur costs and expenses from multiple directions which will result in losses in profit.
— Bahram Khandan (@PivotalStorage) November 9, 2014
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