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54. VIRTUALIZATION (CONTAINERS): PART 2

REVIEW OF VIRTUAL MACHINES (TYPE 1 and TYPE2 HYPERVISORS)

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  • VIRTUAL MACHINES (VMs) allow multiple OS’s to run on a single PHYISCAL SERVER

  • A HYPERVISOR is used to manage and allocate HARDWARE RESOURCES to each VM

    • TYPE 1 HYPERVISORS (aka NATIVE or BARE-METAL) run directly on top of HARDWARE
    • TYPE 2 HYPERVISORS (aka HOSTED) run on top of a HOST OS (ie: WINDOWS)

  • TYPE 1 HYPERVISORS are widely used in DATA CENTER ENVIRONMENTS

  • TYPE 2 HYPERVISORS are commonly used on personal DEVICES

    • Running a virtual network lab on your PC using Cisco Modeling Labs (CML)

  • The OS in each VM can be the same or different (Windows, Linux, MacOS, etc)

  • Bins / Libs are the SOFTWARE libraries / services needed by the Apps running in each VM

  • A VM allows it’s app / apps to run in an ISOLATED environment, separate from the apps in other VMs.

  • VMs are easy to create, delete, move, etc.

    • A VM can be easily saved and moved between different physical SERVERS.

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CONTAINERS

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  • CONTAINERS are software packages that contain an APP and all dependencies (Bins/Libs in the diagram) for the contained APP to run.
    • Multiple APPS can be run in a single CONTAINER, but this is not how CONTAINERS are usually used
  • CONTAINERS run on a CONTAINER ENGINE (ie: DOCKER ENGINE)
    • The CONTAINER ENGINE is run on a HOST OS (usually LINUX)
  • CONTAINERS are lightweight (small in size) and include only the dependencies required to run the specific APP
  • A CONTAINER ORCHESTRATOR is a software platform for automating the DEPLOYMENT, MANAGEMENT, SCALING, etc of CONTAINERS
    • KUBERNETES (originally design by Google) is the most popular CONTAINER ORCHESTRATOR
    • DOCKER SWARM is DOCKER’S CONTAINER ORCHESTRATION tool
  • In small numbers, MANUAL operation is possible, but large-scale systems (ie: with Microservices) can require THOUSANDS of CONTAINERS

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VIRTUAL MACHINES vs. CONTAINERS

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  • VMs can TAKE MINUTES to boot up as each VM runs it’s own OS

  • CONTAINERS can boot up in milliseconds

  • VMs take MORE disk space (Gigabytes)

  • CONTAINERS take up VERY LITTLE disk space (Megabytes)

  • VMs use MORE CPU/RAM resources (each VM must run its own OS)

  • CONTAINERS use FEWER CPU/RAM resources (shared OS)

  • VMs are PORTABLE and can MOVE between physical systems running the same HYPERVISOR

  • CONTAINERS are MORE portable; they are SMALLER, FASTER to boot up, and DOCKER CONTAINERS can be run on nearly ANY CONTAINER SERVICE

  • VMs are more isolated because each VM runs it’s own OS

  • CONTAINERS are less isolated because they all run on the same OS; if the OS crashes, all CONTAINERS running on it are effected

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