Virtualization:
Need grows.......Effort to manage "resource required" for the need grows...........Requirement of flexibility grows...........Requirement of Scalability grows..........Virtualization is the solution to this problem............Though this is need not to be managed by individual, the service providers takes care of these for you.Let start with it......
First thing, Virtualization itself is not cloud, but a part of it or we can say one of the pillar of it.
Virtualization is providing virtual interface of something, here we talk about computing resources, like CPU, Memory, Network components, Storage, etc. Virtualization enables in utilizing the system resources at its best. One large server can server multiple Virtual servers, thus multiple applications running on the same server independently.
There are basically two types of Virtualization:
- Hardware Virtualization
- Software assisted Virtualization
Here we talk about Hardware Virtualiztion
There are different type of Hardware Virtualization:
- Para-virtualization:
- This model of Virtualization eliminates the overhead of trapping-and-emulation caused with software implemented Virtualization. In this model the guest operating system needs to be recompiled or modified before it is installed inside the virtual machine.
- Examples: Xen, VMWare ESX Server
- Guest OS is aware that it is in virtuaized Environment
- Full Virtualization:
- This model of Virtualization contains functionality to emulate the hardware when necessary. Here Hypervisor itself “trap” the machine operations(like to read or modify the system’s status or perform I/O operations). After it has trapped them, the hypervisor emulates these operations in software and returns status codes consistent with what the real hardware would deliver.
- No modification is required in Guest OS to run on this Model of Virtualization.
- Guest OS in unaware of that it is in virtualized Environment.
- Hardware assisted Virtualization:
- This type of Virtualization is Provided by specially designed CPUs(Intel-VT, AMD-v)
- This is based on hardware extensions to the x86 system architecture to eliminate much of the hypervisor overhead associated with trapping and emulating I/O operations and status instructions executed within a guest OS.
- Guest OS need not modified to run on this model of virtualization.
- Kernel Level Virtualization:
- This type of virtualization does not require a hypervisor, but instead runs a separate version of the Linux kernel and an associated virtual machine as a "user–space" process on the physical host.
- This provides an easy way to run multiple virtual machines on a single host.
- KVM uses a device driver in the host’s kernel for communication between the main Linux kernel and the virtual machines.
- This requires processor support for virtualization (Intel-VT or AMD–v) and uses a slightly modified QEMU process as the display and execution container for its virtual machines.
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