Belkin XM Commander Manuel d'utilisateur télécharger pdf (Page 10)

Server consolidation. Move multiple servers onto a single physical host with perfor-

mance and fault isolation provided at virtual machine boundaries.

Cluster computing. Management at VM granularity provides more ﬂexibility than

separately managing each physical host, but better control and isolation than

single-system image solutions, particularly by using live migration for load bal-

ancing.

Hardware support for custom OSes. Allow development of new OSes while bene-

ﬁting from the wide-ranging hardware support of existing OSes such as Linux.

1.1 Structure of a Xen-Based System

A Xen system has multiple layers, the lowest and most privileged of which is Xen

itself. Xen in turn may host multiple guest operating systems, each of which is exe-

cuted within a secure virtual machine (in Xen terminology, a domain). Domains are

scheduled by Xen to make effective use of the available physical CPUs. Each guest

OS manages its own applications, which includes responsibility for scheduling each

application within the time allotted to the VM by Xen.

The ﬁrst domain, domain 0, is created automatically when the system boots and has

special management privileges. Domain 0 builds other domains and manages their

virtual devices. It also performs administrative tasks such as suspending, resuming

and migrating other virtual machines.

Within domain 0, a process called xend runs to manage the system. Xend is responsible

for managing virtual machines and providing access to their consoles. Commands are

issued to xend over an HTTP interface, either from a command-line tool or from a web

browser.

1.2 Hardware Support

Xen currently runs only on the x86 architecture, requiring a ‘P6’ or newer processor

(e.g. Pentium Pro, Celeron, Pentium II, Pentium III, Pentium IV, Xeon, AMD Athlon,

AMD Duron). Multiprocessor machines are supported, and we also have basic support

for HyperThreading (SMT), although this remains a topic for ongoing research. A port

speciﬁcally for x86/64 is in progress, although Xen already runs on such systems in 32-

bit legacy mode. In addition a port to the IA64 architecture is approaching completion.

We hope to add other architectures such as PPC and ARM in due course.

Xen can currently use up to 4GB of memory. It is possible for x86 machines to address

up to 64GB of physical memory but there are no current plans to support these systems:

The x86/64 port is the planned route to supporting larger memory sizes.

Xen ofﬂoads most of the hardware support issues to the guest OS running in Domain 0.

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 55 56

Pas de commentaire

Belkin XM Commander Manuel d'utilisateur Page 10