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  • POPF doesn’t trap if executed with insufficient privilege
  • disk is easy new IO isn’t as fast as not all ring 0 ; win big time

PPT PPT Presentation Transcript

  • 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
    • 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
    • Enforce security policy
    X X
  • 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…)
  • 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 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
  • 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”)