Xen Overview for Campus Grids

1
Xen Overview for Campus Grids

• Andrew WarfieldUniversity of Cambridge
• andrew.warfield_at_cl.cam.ac.uk

Computer Laboratory
2
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

3
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

4
Virtualization in the Enterprise

• Consolidate under-utilized servers to reduce
  CapEx and OpEx

X

• Avoid downtime with VM Relocation

• Dynamically re-balance workload to guarantee
  application SLAs

X

• Enforce security policy

5
Why Xen is interesting for Grid/E-Science
Environments

• Encapsulation
• OS as management primitive, and strong isolation
• Accounting
• Collect detailed usage data on each VM
• Pre-emption and Checkpointing
• Using suspend/resume
• Load Balancing
• Using migration
• Storage virtualization
• Simple virtual block interface can be mapped
• to whatever you like (disk/file/etc)

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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

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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.

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Xen 3.0 Architecture
VM3
VM0
VM1
VM2
Device Manager Control s/w
Unmodified User Software
Unmodified User Software
Unmodified User Software
GuestOS (XenLinux)
GuestOS (XenLinux)
GuestOS (XenLinux)
Unmodified GuestOS (WinXP))
AGP ACPI PCI
Back-End
Back-End
SMP
Native Device Driver
Native Device Driver
Front-End Device Drivers
Front-End Device Drivers
VT-x
Event Channel
Virtual MMU
Virtual CPU
Control IF
Safe HW IF
32/64bit
Xen Virtual Machine Monitor
Hardware (SMP, MMU, physical memory, Ethernet,
SCSI/IDE)
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System Performance
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
L
X
V
U
L
X
V
U
L
X
V
U
L
X
V
U
SPEC INT2000 (score)
Linux build time (s)
OSDB-OLTP (tup/s)
SPEC WEB99 (score)
Benchmark suite running on Linux (L), Xen (X),
VMware Workstation (V), and UML (U)
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TCP results
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
L
X
V
U
L
X
V
U
L
X
V
U
L
X
V
U
Tx, MTU 1500 (Mbps)
Rx, MTU 1500 (Mbps)
Tx, MTU 500 (Mbps)
Rx, MTU 500 (Mbps)
TCP bandwidth on Linux (L), Xen (X), VMWare
Workstation (V), and UML (U)
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Scalability
1000
800
600
400
200
0
L
X
L
X
L
X
L
X
2
4
8
16
Simultaneous SPEC WEB99 Instances on Linux (L)
and Xen(X)
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Web Server Relocation
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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.

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Existing GRID Users

• Tim Freeman and Kate Keahey at Argonne National
  Lab in Chicago
• Looking at combining virtualization with GRID
• Environment creation, management, etc.

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Other Xen Supporters
Operating System and Systems Management
Hardware Systems
Platforms I/O
Logos are registered trademarks of their owners
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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

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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)