Virtualisation | EPFL Graph Search

La virtualisation consiste, en informatique, à exécuter sur une machine hôte, dans un environnement isolé, des systèmes d'exploitation — on parle alors de virtualisation système — ou des applications — on parle alors de virtualisation applicative. Ces ordinateurs virtuels sont appelés serveur privé virtuel (Virtual Private Server ou VPS) ou encore environnement virtuel (Virtual Environment ou VE). Virtualisation des données La virtualisation des données est une approche permettant d'unifier les données de plusieurs sources dans une même couche afin que les applications, les outils de génération de rapports et les utilisateurs finaux puissent accéder aux données sans avoir besoin de détails sur la source, l'emplacement et les structures de données d'origine. Principe Il peut sembler a priori étrange de simuler d'autres machines sur une machine hôte : un système d'exploitation est conçu pour utiliser du matériel qui est entièrement sous son contrôle. La juxtapo

HAVC-II - Idiap Private Cloud (Technical Inside-Out)

Virtualizing resources – servers, storage, networks – is now part of every IT departments life. The benefits of virtualization no longer need to be demonstrated and, when played upon in a large scale, provide both the saddle and spurs with which the Cloud mantra has been riding towards its success. This document shall describe how Idiap took advantage of its infrastructure to build its own virtualization farm, which shall (shamelessly) be referred to as Idiap Private Cloud.

Idiap2015

Traffic Locality as an Opportunity in the Data Center

Jonas Fietz

In large scale data centers, network infrastructure is becoming a major cost component; as a result, operators are trying to reduce expenses, and in particular lower the amount of hardware needed to achieve their performance goals (or to improve the performance achieved for a given amount of hardware). In this thesis, we explore the use of locality in the data center to meet these demands. In particular, we leverage locality in two different projects: (1) VNToR, which moves network virtualization from the server to the top-of-rack (ToR) switch, thereby reducing the server hardware needed to achieve a certain performance, and (2) Criss-Cross, which makes the network topology reconfigurable, thereby reducing the network hardware needed to switch typical data center workloads with a given level of performance. VNToR exploits the locality of traffic flows as well as their long-tailed behavior in the design of a virtual flow table, which extends the hardware flow table of off-the-shelf top-of-rack switches. VNToR uses this virtual flow table in a hybrid data plane that consists of both a hardware as well as a software data plane. This way it can (1) store tens or even hundreds of thousands of access rules, (2) adapt to traffic-pattern changes, typically in less than one millisecond, and (3) uses only commodity switching hardware with a minimal amount of data path memory (4)~without compromising latency or throughput. Criss-Cross is a hierarchical, reconfigurable topology for large-scale data centers. The locality in rack-level flows allows Criss-Cross to adjust its topology to the current traffic patterns. We show that Criss-Cross preserves many of the advantages of Clos topologies: (1) it maintains their hierarchy, (2) the simple routing algorithms, (3) their regular layout of connections for simple physical deployability, and (4) the compatibility to existing management approaches. We demonstrate that for a group-based communication pattern, Criss-Cross improves the average flow completion time by 5.5x and the 99th percentile by 6.3x. For a purely random point-to-point traffic pattern, it improves the flow completion time by 2.2x on average and 3x at the 99th percentile.

EPFL2019

Optimizing network performance in virtual machines

Aravind Menon

In recent years, there has been a rapid growth in the adoption of virtual machine technology in data centers and cluster environments. This trend towards server virtualization is driven by two main factors: the savings in hardware cost that can be achieved through the use of virtualization, and the increased flexibility in the management of hardware resources in a cluster environment. An important consequence of server virtualization is the negative impact it has on the networking performance of server applications running in virtual machines (VMs). In this thesis, we address the problem of efficiently virtualizing the network interface in Type-II virtual machine monitors. In the Type-II architecture, the VMM relies on a special, 'host' operating system to provide the device drivers to access I/O devices, and executes the drivers within the host operating system. Using the Xen VMM as an example of this architecture, we identify fundamental performance bottlenecks in the network virtualization architecture of Type-II VMMs. We show that locating the device drivers in a separate host VM is the primary reason for performance degradation in Type-II VMMs, because of two reasons: a) the switching between the guest and the host VM for device driver invocation, and, b) I/O virtualization operations required to transfer packets between the guest and the host address spaces. We present a detailed analysis of the virtualization overheads in the Type-II I/O architecture, and we present three solutions which explore the performance that can be achieved while performing network virtualization at three different levels: in the host OS, in the VMM, and in the NIC hardware. Our first solution consists of a set of packet aggregation optimizations that explores the performance achievable while retaining the Type-II I/O architecture in the Xen VMM. This solution retains the core functionality of I/O virtualization, including device driver execution, in the Xen 'driver domain'. With this set of optimizations, we achieve an improvement by a factor of two to four in the networking performance of Xen guest domains. In our second solution, we move the task of I/O virtualization and device driver execution from the host OS to the Xen hypervisor. We propose a new I/O virtualization architecture, called the TwinDrivers framework, which combines the performance advantages of Type-I VMMs with the safety and software engineering benefits of Type-II VMMs. (In a Type-I VMM, the device driver executes directly in the hypervisor, and gives much better performance than a Type-II VMM). The TwinDrivers architecture results in another factor of two improvements in networking performance for Xen guest domains. Finally, in our third solution, we describe a hardware based approach to network virtualization, in which we move the task of network virtualization into the network interface card (NIC). We develop a specialized network interface (CDNA) which allows guest operating systems running in VMs to directly access a private, virtual context on the NIC for network I/O, bypassing the host OS entirely. This approach also yields performance benefits similar to the TwinDrivers software-only approach. Overall, our solutions help significantly bridge the gap between the network performance in a virtualized environment and a native environment, eventually achieving network performance in a virtual machine within 70% of the native performance.

EPFL2009