Understanding Networking and Server Visualization
Introduction to Virtualization
Virtualization and Cloud Computing are not same. Its a component of Cloud Computing.
In virtualization there is a separation of OS with the underlying H/W where as in Cloud Computing (CC), there is a separation of Application from the underlying hardware.
- Earlier, OS’s are installed directly on the hardware.
- Virtualization gives a layer of hypervisor, on which an “instances” of OS runs.
- install a hypervisor layer and then install the “Guest OS”
- Can literally move (copy an image and paste) one instance of OS from one server to another without any installation!!
- Also, multiple instances of OS can be installed on hypervisor
Type 1 Hypervisor (Native or Bare Metal) : A physical machine, and hypervisor on it.
Type 2 Hosted hypervisor : Comp. with an OS, and onto that hypervisor is installed eg :VMWare (installed according to the OS). Onto it guest OS are installed
Hosted solutions (Proprietary ones) on Amazon Cloud etc.
you need a management console to interact with hypervisor(once the physical server has an IP address). With the management console, you can move the instances of OS’s among different physical servers.
Also, according to resource needs, management console can migrate (or turn on and off) based on loads (balances the electricity consumption)
If the physical hardware running the hypervisor fails, management console can quickly migrate the OS to another hardware.
Over Allocation : static (RAM is split between all the OS instances) and
dynamic (logical allocation more than the physical)
Most of the hypervisor software are free (most of them based on XEN) but they charge for the management console software.
Careful with type 2 Hypervisor : Be careful of the resource allocation. if 4 GB’s of RAM is allocated, the type 2 virtualization hypervisor will take all 4 GB and allocate to the VM even if its not needed. Can crash host OS by overallocating its hardware resources.