Major Project-Xen

1. Submitted To: Mr. Prakash Kumar
Submitted by:
Nikita Gupta-10103526
Shubham Jain-10103489
Deadline Based Scheduling Technique for
Xen

2. What Is Cloud Computing?
• Cloud computing is a type of computing that relies on sharing
computing resources rather than having local servers or
personal devices to handle applications.
• In cloud computing, the word cloud (also phrased as "the cloud")
is used as a metaphor for "the Internet," so the phrase cloud
computing means "a type of Internet-based computing," where
different services such as servers, storage and applications are
delivered to an organization's computers and devices through
the Internet.
• Cloud computing is comparable to grid computing, a type of
computing where unused processing cycles of all computers in a
network are harnesses to solve problems too intensive for any
stand-alone machine.

3. What is Virtualization?
 Virtualization enables the running of multiple
operating systems on a single machine
 Each Virtual Machine (VM) is isolated and
protected from each other - Illusion of dedicated
physical machine
 Allows an abstraction of server workloads
 Motivation:
 Take advantage of idle machine time
 Easy to maintain and upgrade VMs

4. Xen Overview
 Developed at Cambridge University
 Allows multiple virtual machines within one physical
machine
 Open Source version available as option with Linux
Distributions
 Text-mode tools (but that is improving)
 Now also provided by XenSource (“Commercial Open
Source”)
 Free XenServer Express (complete distribution –
currently 32-bit only)
 Nice graphical tools

5. Domains
 Xen refers to virtual machines as domains
 The host OS runs in a special domain called
 domain-0 (Dom0)
 The guest OSes run in User Domains (DomUs).
 Domains have a domain number and a domain
name.
– Name is fixed; number varies (except for Dom0)
 But all Domains are guests of the Hypervisor

6. Virtualization at the OS Level
 Not based on host/guest paradigm
 Host runs a single OS kernel as its core and
exports OS functionality to each of the guests
 Guests must use the same OS as the host,
although different distributions of the same
system are allowed
 This distributed architecture eliminates system
calls between layers, which reduces CPU
usage overhead

7. Full Virtualization
 Hardware Virtual Machines
 VMWare, Xen HVM, KVM, Microsoft VM,
Parallels
 Runs unmodified guests
 Generally worst performance, but often acceptable
 Simulates bios, communicates with VMs through
ACPI emulation, BIOS emulation, sometimes
custom drivers
 Can sometimes virtualize across architectures,
although this is out of fashion.

8. Para-virtualization
 Hypervisor runs on the bare metal. Handles CPU scheduling
and memory compartmentalization.
 Dom0, a modified Linux Kernel, handles networking and
block storage for all guests.
 Dom0 is also privileged to manage the VMs on the system.
 DomU, or the guests OS, sends some requests straight to the
hypervisor, and others to the Dom0.
 Because the kernel knows its virtualized, features can be built
into it: hot connection/disconnection of resources, friendly
shutdown, serial console.
 Other para virtualization schemes: Sun Logical Domains,
VMware (sometimes)

9. The Para virtual Machine Model
 Also based on host/guest paradigm and uses a
virtual machine monitor
 But here the VMM actually modifies the guest
operating system’s code
 This is called porting
 Porting supports the VMM so it can utilize
privileged systems calls sparingly
 Xen and UML are examples of this model

10. QQ
UU
EE
RR
II
EE
SS
??