SLA Management in Storage Clouds

SLA Management in Storage Clouds

Nikoletta Mavrogeorgi (National Technical University of Athens, Greece), Spyridon V. Gogouvitis (National Technical University of Athens, Greece), Athanasios Voulodimos (University of West Attica, Athens, Greece) and Vasilios Alexandrou (National Technical University of Athens, Greece)
Copyright: © 2013 |Pages: 22
DOI: 10.4018/978-1-4666-3934-8.ch006
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The need for online storage and backup of data constantly increases. Many domains, such as media, enterprises, healthcare, and telecommunications need to store large amounts of data and access them rapidly any time and from any geographic location. Storage Cloud environments satisfy these requirements and can therefore provide an adequate solution for these needs. Customers of Cloud environments do not need to own any hardware for storing their data or handle management tasks, such as backups, replication levels, etc. In order for customers to be willing to move their data to Cloud solutions, proper Service Level Agreements (SLAs) should be offered and guaranteed. SLA is a contract between the customer and the service provider, where the terms and conditions of the offered service are agreed upon. In this chapter, the authors present existing SLA schemas and SLA management mechanisms and compare various features that Cloud providers support with existing SLAs. Finally, they address the problem of managing SLAs in cloud computing environments exploiting the content term that concerns the stored objects, in order to provide more efficient capabilities to the customer.
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In this chapter, we consider SLA for storage cloud services which store and manage the data for customers by a third party.

The SLA is the service level agreement between the user and the service provider, where the level of a service is formally defined. Some of the elements that are defined in the SLAs are the parties involved, the contract date, the terms of agreement and the data cost. The properties that are used in the terms of agreement can be divided in functional and non-functional. The latter can contain quantitative (e.g. availability, durability, latency) and qualitative properties (e.g. adherence to safety properties and absence of deadlocks and livelocks). The quantitative properties are constrained through thresholds, commonly named as Service level objectives (SLOs).

A lot of research and protocols have been done as far as Service Level Agreements (SLA) and the SLA Management are concerned.

SLA schemas are XML schemas that represent the content of an SLA. Some existing approaches for SLA schemas and the corresponding languages to define service description terms are: WS-Agreement (Andrieux, et al., 2005), SLAng (Lamanna, et al.., 2003), WSLA (Keller & Ludwig, 2003), WSOL (Tosic, et al., 2003), and SWAPS (Oldham, et al., 2006).

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