Virtualization Technologies XEN KVM Hypervisor


Virtualization : is a creating of virtual rather than actual real version (Server ,Network ,Storage).virtualization either interact with base os or hardware.

Hypervisor: Also called Virtual Machine Manager (VMM) , Hardware Virtualization . Allowing multiple operating systems termed GUEST OS run concurrently on HOST machine.

1)For Live Migration we need
a) Extra IP
b) Shared Storage
c) Global File system.
NOTE: XEN is the best virtualization.
2) Virtualization Disadvantage

1) Don’t have console block access to trouble shoot.
3) Important Abbreviation & Commands
Virt-manager –GUI managing Virtualization
Virt-viewer –view the console
libirt-actual hypervisor
qemu-kvm ---CLI
/var/libvirt/images - virtualization image. Location
QEMU-Quick Emulator
PAE- Physical Address Extension ( Vmx intel (or) svm AMD)

Required rpm packages are - kernel-xen|xen|libvirt|virt-manager.
Services Are – libvirtd, xend,
#virsh list -all

without OS , install direct in to the hardware ( Linux KVM-directly run on the HW,IBM z/VM,VMware ESX)
with OS, additional Install Virtualization Software.(VMware workstation,VMware server)
Hybrid hyper visor
Domain-0: Privileged domain.( Base OS).
Domain-U/Guest Domains/User Domain: VM created by Dom-0.

Para virtualization(PVM)
Super Visor - Xen Full virtualization (HVM -Hardware Virtual Machine)
Does not emulate hardware (not identical to that underlying hardware).
Emulate the complete hardware virtualization (FULL Virtualization). All the hardware features are reflecting in to the virtual machine.
Does not require the Virtualization extension.
Require Virtualization Extension from Host CPU(Intel VT,AMD -V)
# egrep ‘(vmx|svm)’ /proc/cpuinfo
Not required any special drivers

Full Virtualization slower than para virtualization required emulation.
NOTE : To boost performance use the special para virtual device driver(PVHVM – PV on HVM drivers) to bypass emulation for disk & network I/O.
[emulate Full PC hardware
BIOS, IDE disk controller, VGA graphics card adapter,USB controller, Network adapter]
Xen,  it will act both PVM and HVM.
KVM (Kernel Module)
1) Kernel Based Virtual Machine.
Part Linux use regular Linux scheduler and memory management.
KVM is better integrating with Linux. It's smaller & faster
RHEL 6 Xen is removed and KVM is introduced.
1) External Hypervisor, Control the machine and divide resource amount guest. it will act as both HVM & PVM.

2) There is no need to install new kernel.
2)new kernel should be installed for example
Grub.conf file(need to load the module instead of initrd)
kernel /xen.gz-2.6.18-238.el5
module /vmlinuz-2.6.18-238.el5xen ro root=LABEL=/1 rhgb quiet
module /initrd-2.6.18-238.el5xen.img
3)kvm does not support paravirtualization for cpu
but support paravitualizaiton for device driver to improve I/O performance. ---- support hvm approach.
3)support para & hvm(hardware virtual machine) approaches.
4)Provide stability & reliability
4)Provide better Performance.
5)there is no locking mechanism is there.
5)enable the locking Mechanism that prevents running same guest on different host.
Note 1) It is implement as module /dev/kvm to setup VM ( qemu-kvm).rpm(qemu-kvm)
Note 2)Direct access to hardware /dev/vdx
Note 3)KVM is much smaller and implemented to user.
1)Life migrations are not safe in KVM. Repeatedly encounter block device corruption. Simple Migration still work without problem.
Libvirt Virtualization API – Virtual Machine Manager offer number of graphical tool work with xen,kvm.There network interface is (virbr0)
Xen & KVM both are hyper visor
Note : Both system are stable I did not encounter crashes related to the hyper visor technology.

ESXi Server
1) ESX it Enterprise level virtualization tool based on hypervisor architecture.
2) ESX we can install directly to the server hardware without required under-LYING OS which makes extremely effectively in terms of performance.
3) it is managed by vmkernel(Linux Kernel).
4) REFER :
ESX server requires special CPU Hardware specification.
5) VMWARE ESX Server - use - VMFS - Virtual Machine File System - LUN ( maintain disk image, including snapshot,
VMware VCB - Vmware Consolidate Backup
1)Vmware Workstation (Hosted on Linux or Windows)
2)Vmware ESX server ( RHEL based service console)
3)Vmware ESXi(Vmkernel Hypervisor, No service console)
Features are
High availability, Live Migration, Power Management, Automatic Load balancing.

RHEV–M (Redhat Enterprise Virtualization Manager)
RHEV-H ( Redhat Enterprise Virtualization Hypervisor)

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