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Utilizing the Xen Hypervisor in business practice

Bryan Fuselier

OSS Benefits

Benefits of OSS

Shared pool of resources

Cost Effective

Modifiable

Shared Resources

Massively expanding list of developers and contributors to draw insider knowledge of specific software

Large user groups to contribute experience and real-world knowledge

Cost Effective

"Free software" is a matter of liberty, not price. To understand the concept, you should think of "free" as in "free speech," not as in "free beer." Free software is a matter of the users' freedom to run, copy, distribute, study, change and improve the software. More precisely, it refers to four kinds of freedom, for the users of the software:

The freedom to run the program, for any purpose (freedom 0).

The freedom to study how the program works, and adapt it to your needs (freedom 1). Access to the source code is a precondition for this.

The freedom to redistribute copies so you can help your neighbor (freedom 2).

The freedom to improve the program, and release your improvements to the public, so that the whole community benefits (freedom 3). Access to the source code is a precondition for this.

Modifiable

Source code is freely available to modify at will either in house or outsourced

What's a Hypervisor

Sits between hardware and operating systems

Allocates Resources

Performs like a hardware system's BIOS

Domain Definition

When we are talking about virtualization, a domain is one of the virtual machines that run on the system. Domain0 is the first domain started by the Xen hypervisor at boot, and will be running a Linux OS. This domain is privileged: it may access the hardware and can run the XenControlTools that manage other domains. These other domains are referred to as DomUs, the U standing for "user". They are unprivileged, and could be running any operating system that has been ported to Xen.

How it Works

Step 1) Inventory of physical resources:

IRQ0IRQ1IRQ2IRQ3

How it Works

Step 2) Inventory of processors:

CPU0CPU1CPU2CPU4

How it Works

Step 3) Assign processors to available resources:

CPU0CPU1CPU2CPU3IRQ0IRQ1IRQ2IRQ3

Node 255How it Works

Step 4) Mask all initialization requests to processors:

CPU0CPU1CPU2CPU4IRQ0IRQ1IRQ2IRQ3

IRCPU0

Node 255How it Works

Step 5) Initialize all processors:

CPU0CPU1CPU2CPU4IRQ0IRQ1IRQ2IRQ3

Node 255How it Works

Step 6) Create Dom0:

CPU0CPU1CPU2CPU4IRQ0IRQ1IRQ2IRQ3

Dom0DomU ControlDirect HW Access

Node 255How it Works

Step 7) Physical Memory Inventory:

CPU0CPU1CPU2CPU4IRQ0IRQ1IRQ2IRQ3

Dom0 Dom0 alloc.: 000000041c000000->0000000420000000 (507904 pages to be allocated)

How it Works

Step 7) Virtual Memory Management:

Dom0Loaded kernel: ffffffff80200000->ffffffff805aee6cInit. ramdisk: ffffffff805af000->ffffffff825af000Phys-Mach map: ffffffff825af000->ffffffff829af000Start info: ffffffff829af000->ffffffff829af49cPage tables: ffffffff829b0000->ffffffff829c9000Boot stack: ffffffff829c9000->ffffffff829ca000TOTAL: ffffffff80000000->ffffffff82c00000ENTRY ADDRESS: ffffffff80200000

How it Works

Step 8) Boot Dom0:

Dom0Dom6Dom5Dom4Dom3Dom2Dom1

How LiquidIQ works

I/O Modules perform a PXE boot from an NFS server hosting it's image issuing DHCP

I/O Modules determine which one will be master

Master IOM builds the active database based on hardware resources it finds installed in the chassis.

Master IOM boots each available compute module with the configuration options set in the database

CM looks up it's configuration in the database and boots each VM with it's configuration options in the database

Xen, OSS & Liquid

Shared resources

Liquid IQ - Computer resources

Xen - Support

OSS - Code development

Cost Effective

power and resources

free (as in speech and beer)

free (as in speech sometimes beer)

Modifiable

on-the-fly VM modification

modifiable source code

modifiable source code

Advantages of Xen

Free (as in speech and beer)

Large support basis (via internet forums and paid support options)

Easily manage multi-client environment from one central location

Limitations of Xen

Lose advanced abilities provided by more well known commercial products

VMWare's VMotion

RAM Over subscription

I/O limitations in heavy operating environments (all hypervisors)

Summary

Open Source provides all the major functionality of standard commercial packages

In the case of Xen, this causes higher cost of management and administration over commercial options

Requires someone with the ability to understand and configure software with a development background

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