Para virtualization(PVM)
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Super Visor - Xen Full virtualization (HVM -Hardware Virtual Machine)
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Does not emulate hardware (not identical to that underlying hardware).
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Emulate the complete hardware virtualization (FULL Virtualization). All the hardware features are reflecting in to the virtual machine.
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Does not require the Virtualization extension.
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Require Virtualization Extension from Host CPU(Intel VT,AMD -V)
# egrep ‘(vmx|svm)’ /proc/cpuinfo
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Not required any special drivers
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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]
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KVM (Kernel Module)
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Xen
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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.
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1) External Hypervisor, Control the machine and divide resource amount guest. it will act as both HVM & PVM.
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2) There is no need to install new kernel.
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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
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3)kvm does not support paravirtualization for cpu
but support paravitualizaiton for device driver to improve I/O performance. ---- support hvm approach.
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3)support para & hvm(hardware virtual machine) approaches.
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4)Provide stability & reliability
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4)Provide better Performance.
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5)there is no locking mechanism is there.
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5)enable the locking Mechanism that prevents running same guest on different host.
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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.
Disadvantage
1)Life migrations are not safe in KVM. Repeatedly encounter block device corruption. Simple Migration still work without problem.
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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.
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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 : http://www.trainsignal.com/blog/wp-content/uploads/2007/12/17.png
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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