Amazon Machine Images(AMIs):

AMI Essentials:

  • A preconfigured package (template) required to launch an EC2 instance, includes an:
    • Operating system.
    • Software packages.
    • Other required settings (root storage type & virtualization type).
  • Amazon Machine Images are used with Auto Scaling to quickly launch new servers on demand, and to quickly recover from disaster.
  • You can create your own AMIs, choose from a list of free AWS/community provided AMIs, or choose one from the marketplace.
AMIs come in three main categories:
  • Community AMIs:
    • Free to use.
    • Generally with these AMIs you are just selecting the OS you want.
  • AWS Marketplace AMIs:
    • Pay to use.
    • Generally comes packaged with additional, licensed software.

  • My AMIs:

    • AMIs that you create yourself.

Virtualization:

  • Virtualization is the process of creating a "virtual" version of something rather than the actual version of that thing.

  • In AWS EC2, virtualization refers to using a "portion" of a server's computing power and storage to setup and run an operating system.

  • Virtualization for EC2 is run using the Xen Hypervisor software.

  • The maintenance of the physical AWS server and the Xen Hypervisor is handled by AWS.

Linux AMI Virtualization Types:

  • HVM AMIs (Hardware Virtual Machine):

    • This virtualization type provides the ability to run an operating system directly on top of a virtual machine without any modification, as if it were run on the bare-mental hardware.

    • The Amazon EC2 host system emulates some or all of the underlying hardware that is presented to the guest.

    • Unlike PV guests, HVM guests can take advantage of hardware extensions that provide fast access to the underlying hardware on the host system.

  • PV AMIs (Paravirtual):

    • Guests can run on host hardware that does not have explicit support for virtualization, but they can NOT take advantage of special hardware extensions such as enhanced networking or GPU processing.

    • Historically, PV guests had better performance than HVM guests in many cases, but because of enhancements in HVM virtualization and the availability of PV drivers for HVM AMIs, this is no longer true.

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