Xen Overview for Campus Grids

Andrew WarfieldUniversity of Cambridgeandrew.warfield@cl.cam.ac.uk

Computer Laboratory

What is hardware virtualization?

Indirect the underlying hardware layer

Allow multiplexing and isolation

Key points: Treat OS as a component Split the administrative role in half

What is Xen?

Virtual machine manager (VMM) Developed at University of

Cambridge An Isolation Kernel Recently included in mainline Linux Used in many production

environments

Virtualization in the Enterprise

X

Consolidate under-utilized servers to reduce CapEx and OpEx

Avoid downtime with VM Relocation

Dynamically re-balance workload to guarantee application SLAs

X Enforce security policyX

Why Xen is interesting for Grid/E-Science Environments

EncapsulationOS as management primitive, and strong isolation

AccountingCollect detailed usage data on each VM

Pre-emption and CheckpointingUsing suspend/resume

Load BalancingUsing migration

Storage virtualizationSimple virtual block interface can be mapped to whatever you like (disk/file/etc…)

Virtualization Overview

Single OS image: Virtuozo, Vservers, Zones Group user processes into resource containers Hard to get strong isolation

Full virtualization: VMware, VirtualPC, QEMU Run multiple unmodified guest OSes Hard to efficiently virtualize x86

Para-virtualization: UML, Xen Run multiple guest OSes ported to special arch Arch Xen/x86 is very close to normal x86

Paravirtualization

Virtualization is traditionally slow relative to raw hardware (IBM VM, VMware, etc)

Xen paravirtualizes Co-design with VM OS Optimize OS to run in a virtualized

environment Maintain ABI – applications stay the

same.

Xen 3.0 Architecture

Event Channel Virtual MMUVirtual CPU Control IF

Hardware (SMP, MMU, physical memory, Ethernet, SCSI/IDE)

NativeDeviceDriver

GuestOS(XenLinux)

Device Manager & Control s/w

VM0

NativeDeviceDriver

GuestOS(XenLinux)

UnmodifiedUser

Software

VM1

Front-EndDevice Drivers

GuestOS(XenLinux)

UnmodifiedUser

Software

VM2

Front-EndDevice Drivers

UnmodifiedGuestOS(WinXP))

UnmodifiedUser

Software

VM3

Safe HW IF

Xen Virtual Machine Monitor

Back-End Back-End

VT-x

32/64bit

AGPACPIPCI

SMP

System Performance

L X V U

SPEC INT2000 (score)

L X V U

Linux build time (s)

L X V U

OSDB-OLTP (tup/s)

L X V U

SPEC WEB99 (score)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

Benchmark suite running on Linux (L), Xen (X), VMware Workstation (V), and UML (U)

TCP results

L X V UTx, MTU 1500 (Mbps)

L X V URx, MTU 1500 (Mbps)

L X V UTx, MTU 500 (Mbps)

L X V URx, MTU 500 (Mbps)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

1.1

TCP bandwidth on Linux (L), Xen (X), VMWare Workstation (V), and UML (U)

Scalability

L X

2L X

4L X

8L X

16

0

200

400

600

800

1000

Simultaneous SPEC WEB99 Instances on Linux (L) and Xen(X)

Web Server Relocation

Performance issues for GRID environments

One problematic workload: Synchronous, low-latency, MPI-style communications. Domain crossings / no batching.

BUT: Hardware vendors know this is a problem that needs fixing. Several vendors are in the process of

building virtualization-friendly devices.

Existing GRID Users

Tim Freeman and Kate Keahey at Argonne National Lab in Chicago

Looking at combining virtualization with GRID Environment creation, management,

etc.

Other Xen Supporters

Hardware Systems

Platforms & I/O

Operating System and Systems Management

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Ongoing Work

Parallax: Distributed VM storage Decentralized, data replication, copy-on-

write Pervasive Debugging

VMs are an ideal debugging environment

XenSE: Security Enhanced Xen MAC-based VMM

Conclusions

Xen is a complete and robust GPL VMM Outstanding performance and scalability Excellent resource control and protection Live relocation makes seamless migration

possible for many real-time workloads

http://www.cl.cam.ac.uk/Research/SRG/netos/xen/(Google for “Xen”)