Synnefo » snf-ganeti

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Glossary

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.. if you add new entries, keep the alphabetical sorting!

.. glossary::

  :sorted:

  ballooning

    A term describing runtime, dynamic changes to an instance's memory,

    without having to reboot the instance. Depending on the hypervisor

    and configuration, the changes need to be initiated manually, or

    they can be automatically initiated by the hypervisor based on the

    node and instances memory usage.

  BE parameter

    BE stands for *backend*. BE parameters are hypervisor-independent

    instance parameters such as the amount of RAM/virtual CPUs it has

    been allocated.

  DRBD

    A block device driver that can be used to build RAID1 across the

    network or even shared storage, while using only locally-attached

    storage.

  HV parameter

    HV stands for *hypervisor*. HV parameters are the ones that describe

    the virtualization-specific aspects of the instance; for example,

    what kernel to use to boot the instance (if any), or what emulation

    model to use for the emulated hard drives.

  HVM

    Hardware virtualization mode, where the virtual machine is oblivious

    to the fact that's being virtualized and all the hardware is

    emulated.

  LogicalUnit

    The code associated with an :term:`OpCode`, e.g. the code that

    implements the startup of an instance.

  LUXI

     Local UniX Interface. The IPC method over :manpage:`unix(7)`

     sockets used between the CLI tools/RAPI daemon and the master

     daemon.

  OOB

    *Out of Band*. This term describes methods of accessing a machine

    (or parts of a machine) not via the usual network connection. For

    example, accessing a remote server via a physical serial console or

    via a virtual one IPMI counts as out of band access.

  OpCode

    A data structure encapsulating a basic cluster operation; for

    example, start instance, add instance, etc.

  PVM

    (Xen) Para-virtualization mode, where the virtual machine knows it's

    being virtualized and as such there is no need for hardware

    emulation or virtualization.

  SoR

    *State of Record*. Refers to values/properties that come from an

    authoritative configuration source. For example, the maximum VCPU

    over-subscription ratio is a *SoR* value, but the current

    over-subscription ration (based on how many instances live on the

    node) is a :term:`SoW` value.

  SoW

    *State of the World*. Refers to values that describe directly the

    world, as opposed to values that come from the

    configuration. Contrast with :term:`SoR`.

  tmem

    Xen Transcendent Memory

    (http://en.wikipedia.org/wiki/Transcendent_memory). It is a

    mechanism used by Xen to provide memory over-subscription.

  watcher

    :command:`ganeti-watcher` is a tool that should be run regularly

    from cron and takes care of restarting failed instances, restarting

    secondary DRBD devices, etc. For more details, see the man page

    :manpage:`ganeti-watcher(8)`.

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