I am not able to understand this hierarchy. Host OS runs on bare metal. Where does libvirt reside ? where does the Hypervisor reside ? Is libvirt a necessary lib in the creation of a VM or is it just a better abstraction to the core kernel APIs that provide the the service of creation of VMs? what is the libvirt equivalent in windows that is used by Virtualbox ? Does Hypervisor have any role to play in the scheduling of host OS applications or is it just another process handled by the Host OS. These are a few questions that confuse me. Can anyone explain this in a straight manner ? Thanks!
Host OS runs on bare metal - Yes
where does the Hypervisor reside? - It is a software layer on Host OS
Where does libvirt reside? - It is another API layer on the Host to indirectly interface with the hypervisor.
Is libvirt a necessary lib in the creation of a VM or is it just a better abstraction to the core kernel APIs that provide the the service of creation of
VMs? - Standard abstraction
What is the libvirt equivalent in windows that is used by Virtualbox ? - Libvirt can be used to interact with VirtualBox. Libvirt is known to work as a client (not server) on Windows XP (32-bit), and Windows 7 (64-bit).
Does Hypervisor have any role to play in the scheduling of host OS applications or is it just another process handled by the Host OS. - Just another process
References: http://virtualbox.guru
Related
What is the difference between bare-metal (hypervisor-based) and host virtualization types ?
A well-known example of a hosted hypervisor is Oracle VM VirtualBox. Others include VMWare Server and Workstation, Microsoft Virtual PC, KVM, QEMU and Parallels.
rest is over here
Can I say openstack is relying on hosted virtualization as KVM,qemu is listed in this branch
bare metal- Metal(hardware)+minimum things required to run an OS. So in that sense, bare metal hypervisor is also hosted.
host virtualization - On the existing host along with your favourite music player, text editor, hypervisor is installed just like an app.
Bare Metal Servers
• Servers that are physical and dedicated to a single tenant
• Bare metal servers are Fast provisioning servers and custom-based servers
• They are Physically isolated, powerful, consistent, scale seamlessly.
• Ted is faster than Virtual servers.
• Bare metal servers can offer better performance and security for certain workloads and are more ideal for heavy workloads.
Host Virtual Server
• Easily deployed, can be created on shared or dedicated infrastructure, customizable, can be provisioned quickly, scalable, and integrated seamlessly.
• Some of the deployment options: public virtual servers, transient virtual servers, and dedicated virtual servers.
• Host Virtual servers provision more quickly and offer a more flexible and scalable environment than bare metal.
Am starting to learn openstack. As per my understanding (after reading all the docs) is that the compute nodes run a host OS (ubuntu or other linux) and on top of that you have your hypervisor (like KVM) and then the VMs run on top of it i.e HW -> OS -> Hypervisor -> VMs . This is similar to having a VM running on Virtualbox which runs on a host operating system i.e HW-> Host OS ->VBox -> VMs.Please correct me if my understanding is incorrect.
Assuming my first understanding is correct, How will the performance of the VMs on the this architecture be compared to running the VMs directly on hypervisor i.e HW-> Hypervisor (KVM)->VMs ?
Comparing this with VMWare openstack architecture where Nova speaking to VMWare vCenter and then vCenter manages the ESXi nodes (vCenter and ESXi are on different nodes). This way my VMs are directly running on top of hypervisor connected to HW (HW->ESXi->VMs).And all the overlay networking is handled by NSX. This looks much more performant compared to the other architecture. Am i missing something here ?
Thanks in advance.
~exp8
Since kvm runs on linux kernel, and runs instructions directly on the cpu, it is the hypervisor (HW -> HyperVisor -> VM). On the VMware side, there is a tiny proprietary tuned version of linux as hypervisor.
To find out which one is more efficient, you should do benchmarking. But if you think Vmware's linux consumes less resources (less process, memory, cpu), it may be better.
I've read this article:
How is Docker different from a normal virtual machine?
I have huge intend of converting all my virtual images into docker instances.
I can't see an angle where vm still make sense...
So what's the point to VM now? Ok... maybe the desktop virtualization to have pulseaudio working?
Once docker solve this, what else?
UPDATE
Okay... So I can't run docker in "non-linux" favour hosts...
For one point you can't run an operating system within your container that is different from the OS on the host.
On Windows and Mac OSX boot2docker is used to run Docker which is VirtualBox running a reduced Linux OS which runs Docker.
The benefits of containers are clear and well known, but the disadvantages have been glossed over somewhat.
Specifically, you don't just need the same OS type (aka linux), you get the same version of the kernel (including any mods you want.) Since containers are an OS construct, there are resource islands per OS kernel version (and different implementations for Windows, BSD or any non-linux if they exist).
VM's are secured with CPU level isolation, containers are secured with OS level isolation (with arguably a bigger attack surface).
There are many claims out there that containers are as slow and as big as VM's once you load up your container with everything you need for production and add lots of overlays, but these are all anecdotal and no large scale survey or trustable data is available yet.
What's the difference between process virtual machine with system virtual machine?
My guess is that process VM is not providing a kind of an operating system for the whole application for that OS, rather providing an environment for some specific application.
And system VM is providing an environment for an OS to be installed just like VirtualBox.
Am I getting it correct?
Another question is the difference between the two different implementation of system VM: hosted vs. stand-alone.
I'm a beginner studying OS, so easy and understandable answer would be greatly appreciated :)
A Process virtual machine, sometimes called an application virtual machine, runs as a normal application inside a host OS and supports a single process. It is created when that process is started and destroyed when it exits. Its purpose is to provide a platform-independent programming environment that abstracts away details of the underlying hardware or operating system, and allows a program to execute in the same way on any platform.
A System virtual machine provides a complete system platform which supports the execution of a complete operating system (OS),Just like you said VirtualBox is one example.
A Host virtual machine is the server component of a virtual machine , which provides computing resources in the underlying hardware to support guest virtual machine (guest VM).
The following is from http://airccse.org/journal/jcsit/5113ijcsit11.pdf :
System Virtual Machines
A System Virtual Machine gives a complete virtual hardware platform with support for execution
of a complete operating system (OS).
The advantage of using System VM are:
Multiple Operating System environments can run in parallel on the same piece of
hardware in strong isolation from each other.
The VM can provide an instruction set architecture (ISA) that is slightly different from
that of the real machine
The main draw backs are:
Since the VM indirectly accesses the same hardware the efficiency is compromised.
Multiply VMs running in parallel on the same physical machine may result in varied
performance depending on the workload imposed on the system. Implementing proper
isolation techniques may address this drawback.
What is your preferred development environment ?
Native
WAMP/MAMP/LAMP (Apache, MySQL, PHP) on Windows/MacOS/Linux
Working copy local, SVN/CVS on server
IDE/Editor on the same system (Eclipse, Aptana, Zend...)
Virtual/Native (Server on VM)
LAMP on VirtualBox/VMware
working copy in the VM
IDE/Editor on host, access to the VM with Samba, FTP, SFTP (eventually mapping with tools like WebDrive)
Virtual (VM)
Complete development environment running in a VM (server, tools, IDE)
Host is only used for special tools not available on the OS running in the VM
All have pros and cons.
With BitNami stacks you can run the exact same XAMP environment locally or remotely (and make sure everybody on your team is running the exact same stack). It is free and works on Windows, Linux, Mac.
I like having the SVN repository somewhere on a web server.
It's reasonably secure (using Apache WebDAV), and it gives me a good chance of recovering quickly from any disasters that may befall my main development machine. I have the luxury of control over my own web server, but there are lots of cheap hosts that will do the job at low cost.
As regards VM or no VM:
Advantages of VM - very fast recovery from screwing up your development environment
Ability to try out different versions or upgrades quickly
If you have many systems running the VM host, ability to quickly move the whole environment
Can choose any Host
Disadvantages of VM - performance impact; extra setup complexity.
On balance, I go for "no VM" if all the tools are available on my host system, but I do use VM when I need to run a different OS (the host system is a Mac Pro, so if I need Visual Studio, I do it with Parallels).