Changes between Version 7 and Version 8 of Paravirtualization


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Timestamp:
Nov 17, 2008, 8:39:16 PM (15 years ago)
Author:
broder
Comment:

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  • Paravirtualization

    v7 v8  
    11Xen supports two different types of virtualization: Hardware-supported virtualization (HVM) and paravirtualization (ParaVM).
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    3 Most xvm VMs are initially created as HVMs. HVMs virtualize a full machine, down to the metal. They use special processor capabilities to do this. This allows you to run an unmodified operating system. For example, this is the only way to run Windows under Xen. However, I/O performance suffers as a result of this virtualization approach.
     3Most XVM VMs are initially created as HVMs. HVMs virtualize a full machine, down to the metal. They use special processor capabilities to do this. This allows you to run an unmodified operating system. For example, this is the only way to run Windows under Xen. However, I/O performance suffers as a result of this virtualization approach.
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    55ParaVMs on the other hand, modify the guest operating system to remove privileged operations, replacing them with calls to the Xen hypervisor. ParaVMs have significantly better performance, but require a modified kernel. Only a few operating systems have support for running as a paravirtualized Xen guest: Linux, NetBSD, OpenBSD, FreeBSD, and !OpenSolaris being the most well known.
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    7 The xvm maintainers recommend that servers be converted to ParaVM when possible. Currently, we can offer instructions for upgrading 64-bit installs of Debian or Ubuntu.
     7Because of the performance benefits, you should consider using a ParaVM if possible.
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    99== Converting a Linux Guest to ParaVM ==