Resource management of replicated service systems provisioned in the cloud

Service providers seek scalable and cost-effective cloud solutions for hosting their applications. Despite significant recent advances facilitating the deployment and management of services on cloud platforms, a number of challenges still remain. Service providers are confronted with time-varying requests for the provided applications, inter- dependencies between different components, performance variability of the procured virtual resources, and cost structures that differ from conventional data centers. Moreover, fulfilling service level agreements, such as the throughput and response time percentiles, becomes of paramount importance for ensuring business advantages.In this thesis, we explore service provisioning in clouds from multiple points of view. The aim is to best provide service replicas in the form of VMs to various service applications, such that their tail throughput and tail response times, as well as resource utilization, meet the service level agreements in the most cost effective manner. In particular, we develop models, algorithms and replication strategies that consider multi-tier composed services provisioned in clouds. We also investigate how a service provider can opportunistically take advantage of observed performance variability in the cloud. Finally, we provide means of guaranteeing tail throughput and response times in the face of performance variability of VMs, using Markov chain modeling and large deviation theory. We employ methods from analytical modeling, event-driven simulations and experiments. Overall, this thesis provides not only a multi-faceted approach to exploring several crucial aspects of hosting services in clouds, i.e., cost, tail throughput, and tail response times, but our proposed resource management strategies are also rigorously validated via trace-driven simulation and extensive experiment

Dataintegritetssdkydd för otillförlitligt lagringsutrymme

Storing information such as data backups or family pictures on third party servers instead of local storage can be conceived as getting increasingly commonplace as more and more providers are starting to offer these services. In this situation, a user may not fully trust the external storage space and may want to verify the integrity of the stored data when it is retrieved, using a small authentication value on local trusted storage. Several cryptographic integrity protection schemes exist for computing the authentication value, the most commonly used being Merkle hash trees. These hash trees incur logarithmic work (in the total number of blocks) for updating and for verifying a block, and a linear amount of additional untrusted storage space. There are also alternative methods such as incremental hashing and dynamic accumulators, where the work required for one operation is constant (updating for incremental hashing, verifying for accumulators), whereas the other operation incurs linear overhead. This project consisted of implementing an integrity checker using incremental hashing and dynamic accumulators, and evaluating the performance of both schemes. The integrity checker was also integrated into an integrity protected file system using the open source project FUSE for implementing file systems in userspace under Linux. The implementation language was Java, and the FUSE integration was done using the FUSE-J Java bindings. This Master's Thesis has been done for IBM Zürich Research Laboratory, Switzerland

Automated Behavioral Phenotyping Reveals Presymptomatic Alterations in a SCA3 Genetrap Mouse Model

Characterization of disease models of neurodegenerative disorders requires a systematic and comprehensive phenotyping in a highly standardized manner. Therefore, automated high-resolution behavior test systems such as the homecage based LabMaster system are of particular interest. We demonstrate the power of the automated LabMaster system by discovering previously unrecognized features of a recently characterized atxn3 mutant mouse model. This model provided neurological symptoms including gait ataxia, tremor, weight loss and premature death at the age of 12 months usually detectable just 2 weeks before the mice died. Moreover, using the LabMaster system we were able to detect hypoactivity in presymptomatic mutant mice in the dark as well as light phase. Additionally, we analyzed inflammation, immunological and hematological parameters, which indicated a reduced immune defense in phenotypic mice. Here we demonstrate that a detailed characterization even of organ systems that are usually not affected in SCA3 is important for further studies of pathogenesis and required for the preclinical therapeutic studies