Nefeli: Hint-Based Execution of Workloads in Clouds

Abstract—Virtualization of computer systems has made feasi-ble the provision of entire distributed infrastructures in the form of services. Such services do not expose the internal operational and physical characteristics of the underlying machinery to either users or applications. In this way, infrastructures including computers in data-centers, clusters of workstations, and networks of machines are shrouded in “clouds”. Mainly through the deployment of virtual machines, such networks of computing nodes become cloud-computing environments. In this paper, we propose Nefeli, a virtual infrastructure gateway that is capable of effectively handling diverse workloads of jobs in cloud environments. By and large, users and their workloads remain agnostic to the internal features of clouds at all times. Exploiting execution patterns as well as logistical constraints, users provide Nefeli with hints for the handling of their jobs. Hints provide no hard requirements for application deployment in terms of pairing virtual-machines to specific physical cloud elements. Nefeli helps avoid bottlenecks within the cloud through the realization of viable virtual machine deployment mappings. As the types of jobs change over time, deployment mappings must follow suit. To this end, Nefeli offers mechanisms to migrate virtual machines as needed to adapt to changing performance needs. Using our prototype system, we show significant improvements in overall time needed and energy consumed for the execution of workloads in both simulated and real cloud computing environments. I

Διαχείριση πόρων σε νέφη υποδομής

In this thesis, we present our work on four fundamental problems current Iaas clouds face: A) how consumers can assist the cloud middleware in resource management while the internal structure of the cloud is never revealed. B) the vm-to-phm placement in large non-homogeneous physical infrastructures.C) load balancing though live vm migration under time constraints while not depleting the cloud resources.D) the maximization of the financial profit when using the cloud. The proposed solutions on these problems show significant improvements in the efficiency of iaas clouds.Στην παρούσα εργασία, εξετάζουμε τέσσερα θεμελιώδη προβλήματα που αντιμετωπίζουν σήμερα τα νέφη υποδομής (iaas-clouds):Α) με ποιο τρόπο ο καταναλωτής μπορεί να βοηθήσει στη διαχείριση των πόρων, ενώ η εσωτερική δομή της υποδομής του νέφους παραμένει κρυφή.Β) η τοποθέτηση των vm-σε-φυσικές μηχανές σε μεγάλα μη ομοιογενή νέφη.Γ) η εξισορρόπηση φορτίου μέσω ζωντανής μετακίνησης vm υπό χρονικούς περιορισμούς, χωρίς αυτό να συνεπάγεται την εξάντληση των πόρων του νέφους.Δ) η μεγιστοποίηση του οικονομικού κέρδους κατά τη χρήση του νέφους. Οι προτεινόμενες λύσεις για τα προβλήματα αυτά δείχνουν σημαντική βελτίωση της αποτελεσματικότητας των νεφών υποδομή

On the efficiency of time-varying channel models

Publication in the conference proceedings of EUSIPCO, Florence, Italy, 200

Adaptive Live VM Migration in Share-Nothing IaaS-Clouds with LiveFS

Live migration is a versatile option when it comes to attain load-balancing in IaaS-cloud architectures. Liveness, reliability and conformance to SLAs may all be achieved by moving a VM that creates excessive work from its current physical machine (PM) to a less busy node. Despite its promising features, live migration is an expensive operation in terms of resources. The situation gets further exacerbated when the movement involves PMs working off different file-systems which is often the case in shared-nothing IaaS-cloud infrastructures. In this paper, we suggest an approach that adapts the migration operation based on the I/O activity of the originating-VM. We introduce LiveFS, a FUSE-file system which traps all I/Os and helps determine how to best ship virtual disk segments across PMs in a share-nothing IaaS-cloud. Through prototyping and experimentation, we show that LiveFS can improve the shipment of VMs for diverse types of workloads. In particular, LiveFS succeeds in reducing the Total Migration Time by up to 64% compared to the “pre-copy” live migration technique. Furthermore during migration, we attain up-to 19% less I/O-delay if compared to the “post-copy” livemigration approach

Time-Constrained Live VM Migration in Share-Nothing IaaS-Clouds

Both economic reasons and interoperation requirements necessitate the deployment of IaaS-clouds based on a share-nothing architecture. Here, live VM migration becomes a major impediment to achieving cloud-wide load balancing via selective and timely VM-migrations. Our approach is based on copying virtual disk images and keeping them synchronized during the VM migration operation. In this way, we ameliorate the limitations set by shared storage cloud designs as we place no constraints on the cloud’s scalability and load-balancing capabilities. We propose a special-purpose file system, termed MigrateFS, that performs virtual disk replication within specified time-constraints while avoiding internal network congestion. Management of resource consumption during VM migration is supervised by a low-overhead and scalable distributed network of brokers. We show that our approach can reduce up to 24% the stress of already saturated physical network links during load balancing operations