Xen Overview for Campus Grids Andrew Warfield University of Cambridge [email_address] Computer Laboratory
What is hardware virtualization?
Indirect the underlying hardware layer
Allow multiplexing and isolation
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
Enforce security policy
Why Xen is interesting for Grid/E-Science Environments
OS as management primitive, and strong isolation
Collect detailed usage data on each VM
Pre-emption and Checkpointing
Simple virtual block interface can be mapped
to whatever you like (disk/file/etc…)
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
Virtualization is traditionally slow relative to raw hardware (IBM VM, VMware, etc)
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 MMU Virtual CPU Control IF Hardware (SMP, MMU, physical memory, Ethernet, SCSI/IDE) Native Device Driver GuestOS (XenLinux) Device Manager & Control s/w VM0 Native Device Driver GuestOS (XenLinux) Unmodified User Software VM1 Front-End Device Drivers GuestOS (XenLinux) Unmodified User Software VM2 Front-End Device Drivers Unmodified GuestOS (WinXP)) Unmodified User Software VM3 Safe HW IF Xen Virtual Machine Monitor Back-End Back-End VT-x 32/64bit AGP ACPI PCI 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 U Tx, MTU 1500 (Mbps) L X V U Rx, MTU 1500 (Mbps) L X V U Tx, MTU 500 (Mbps) L X V U Rx, 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 2 L X 4 L X 8 L 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 * Logos are registered trademarks of their owners Acquired by
Parallax: Distributed VM storage
Decentralized, data replication, copy-on-write
VMs are an ideal debugging environment
XenSE: Security Enhanced Xen
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