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KVM is #4 ranked solution in best Server Virtualization Software. PeerSpot users give KVM an average rating of 7.6 out of 10. KVM is most commonly compared to Proxmox VE: KVM vs Proxmox VE. KVM is popular among the large enterprise segment, accounting for 56% of users researching this solution on PeerSpot. The top industry researching this solution are professionals from a comms service provider, accounting for 30% of all views.
Buyer's Guide

Download the Server Virtualization Software Buyer's Guide including reviews and more. Updated: September 2022

What is KVM?
KVM (for Kernel-based Virtual Machine) is a full virtualization solution for Linux on x86 hardware containing virtualization extensions (Intel VT or AMD-V). It consists of a loadable kernel module, kvm.ko, that provides the core virtualization infrastructure and a processor specific module, kvm-intel.ko or kvm-amd.ko.
KVM Customers
MediaWiki, Wikimedia Foundation, Wikipedia, Wikivoyage, Wikidata, Wikiversity, Commons

Archived KVM Reviews (more than two years old)

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Ernesto HernáNdez - PeerSpot reviewer
Project Leader at Logicalis
MSP
Easy to manage with a central interface, but the setup process can be improved
Pros and Cons
  • "The KVM service is well managed with a central policy interface."
  • "The initial setup of this solution is more difficult than some of the competing products and it could be improved."

What is our primary use case?

We are an integrator and this is one of the solutions that we implement for our clients. I have more than twenty years of experience working with these kinds of technologies.

We are using this solution for virtualization on IBM servers.

What is most valuable?

KVM is a very good solution for the user ecosystem.

The KVM service is well managed with a central policy interface.

What needs improvement?

The initial setup of this solution is more difficult than some of the competing products and it could be improved.

I would like to be able to see virtual networking integrated with the virtual machine.

For how long have I used the solution?

We have been using KVM for more than five or six years.

Buyer's Guide
Server Virtualization Software
September 2022
Find out what your peers are saying about KVM, Oracle, Microsoft and others in Server Virtualization Software. Updated: September 2022.
632,779 professionals have used our research since 2012.

What do I think about the stability of the solution?

We have experienced some strange problems with instability using KVM. If you install a new driver, HBA, or a new PC network adapter, then you can have problems because of the process of certification for these devices. It happens because KVM is a solution that supports many different kinds of hardware, unlike VMware which is much more restrictive in terms of what it is compatible with. The problem with having such an open solution is that it can also be the cause of issues with stability.

What do I think about the scalability of the solution?

The scalability of KVM is not as good as that of VMware. 

We have approximately twenty people who are using this solution.

Which solution did I use previously and why did I switch?

We were using VMware prior to KVM. It is a very reliable and very strong solution, but it is also very expensive. We are switching to try and reducts cost both in terms of licensing and managing.

How was the initial setup?

The initial setup is more difficult than some other products, such as Nutanix. However, it is easier and more compact than the VMware setup.

What about the implementation team?

We implement KVM for our clients and we have a technical support team of about fifteen people.

What other advice do I have?

The most important thing for people to do when they are researching this kind of solution is to try and understand the main reason and concerns behind virtualization. They should learn the strong points and weakness of this technology, and try to have a base knowledge to understand the concept and how it can be used and managed on a daily basis.

I would rate this solution a seven out of ten.

Which deployment model are you using for this solution?

Private Cloud
Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
VascoCampos - PeerSpot reviewer
System Engineer at NoBoring Lda
Real User
Open Source Virtualization that works with Linux
Pros and Cons
  • "I like that this is an open-source solution. It is very powerful, and it's easy."
  • "The virtual manager and the graphical QEMU for KVM need some improvement."

What is our primary use case?

I am using this solution in my home lab because I don't know this solution well enough to put it into production. I have many clients, and by putting KVM into production it would require several changes, which would require more experience.

In the meantime, I will continue to use VMware and ESXi.

I use both on-premises and cloud-based deployment models. I typically use this solution on the cloud because I have many dedicated servers. However, I also use it on low-powered hardware machines, like old laptops, to create a firewall, access the router, or use as an access point.

What is most valuable?

I like that this is an open-source solution. It is very powerful, and it's easy.

When you install Hypervisor with KVM, you can transform it into a server with the graphical QEME in minutes, then look at what you have and remove all graphical things and then you can restore what you had originally.

What needs improvement?

The virtual manager and the graphical QEMU for KVM need some improvement.

In the next release, I would like to see some changes made to the dashboard as it would be nice to see some icons and some graphics when you are showing this solution to clients.

MOP made some changes to the dashboard, but it made it more difficult and it's a bit complicated. Maybe this was done intentionally because this is an open-source solution with technical support as an additional fee.

For how long have I used the solution?

I have been using this solution for more than three years.

What do I think about the stability of the solution?

This solution is very stable.

It's straightforward and recoverable, it's easy to do anything.

What do I think about the scalability of the solution?

This solution is scalable. Ubuntu is the best version to scale because with the MAS you can set load balancing, and they offer a free account to manage the load balancing for up to ten servers.

Currently, I am the only user.

How are customer service and technical support?

I haven't contacted technical support.

Which solution did I use previously and why did I switch?

I have been using VMware, ESXi, and Linux and will continue to use them while I get more experience with KVM.

How was the initial setup?

The initial setup is straightforward.

There is a lot of information available online. You can do it all by yourself, you just need the time and the will to do it.

What's my experience with pricing, setup cost, and licensing?

This solution is an open-source, free platform with paid support.

What other advice do I have?

You can virtualize anything now, but in my experience, they are good for Linux and Unix systems. I have also used Windows.

Even if you are using another platform hypervisor, as I do with VMware, you may get yourself in a situation where you want to install the KVM or at least the key tools. You can access RAM drives, or broken virtual hard drives, or migrate them to another type of hard drive.

KVM is very complete, it is very powerful, but people are used to graphical QEMU and that is an issue.

The solution performs well and has many tools. It offers everything that all other paid versions have. Everything is in your hands, all you need is the internet to access all of the information on KVM.

I would rate this solution a nine out of ten.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
Buyer's Guide
Server Virtualization Software
September 2022
Find out what your peers are saying about KVM, Oracle, Microsoft and others in Server Virtualization Software. Updated: September 2022.
632,779 professionals have used our research since 2012.
Georges ESSOMBA - PeerSpot reviewer
Business Engineer and Consultant at All-Tech
Real User
Top 20
A solution with an easy initial setup that's scalable and stable
Pros and Cons
  • "Scaling the solution is easy. You just have to add more hardware."
  • "The solution should be more user friendly. We are struggling with the command lines."

What is our primary use case?

We primarily use it to write the payroll solution fort Windows Server 2012 and 2018.

What is most valuable?

The solution is very light when you are putting your Operating System on it. You forget that there's a virtual layer on your solution. You are using it as if it was a whole computer. It's like having an entire computer that you've launched and have running with the Operating System that you need to work with.

What needs improvement?

The solution should be more user friendly despite that some interesting graphical solutions are available to manage the VMs. it would be usefull that the solution integrate the VM snapshot features and make it graphical, so we have a VM infrastructure more complete and easy the backup/restore in case of issue.

For how long have I used the solution?

I've been using the solution since 2014.

What do I think about the stability of the solution?

The solution is very stable. It's been stable since I started using it in 2014.

What do I think about the scalability of the solution?

Scaling the solution is easy. You just have to add more hardware.

How are customer service and technical support?

I've never needed to contact technical support. To me, that's a sign of a good solution.

How was the initial setup?

The initial setup is easy. There is a lot of documentation online, so if there is a problem the online information will help you. 

Deployment only took one hour.

What about the implementation team?

I handled the implementation myself.

What other advice do I have?

We're using the on-premises deployment model. We're using the community version of the solution.

I'd rate the solution nine out of ten.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
Principal Engineer at a financial services firm with 1,001-5,000 employees
Real User
Top 20
Simple to set up and has good Linux support

What is our primary use case?

We are no longer using this solution. We evaluated it, but I have not used it in a production environment.

This solution is used for virtualization.

We have an on-premises deployment.

How has it helped my organization?

same features that vmware have concerning disaster recovery, high availibility and live motion of vm

What is most valuable?

simplicity of installation

What needs improvement?

full interoprability with vm format (ova, ovf, ..) for been aable to move forward or backward to another virtualization solution

What do I think about the scalability of the solution?

We did not test scalability during our evaluation.

Which solution did I use previously and why did I switch?

We are currently using VMware in our production environment.

How was the initial setup?

The initial setup of this solution is quite simple.

Which other solutions did I evaluate?

no.
Vmware fitted best with our technolgy stack (DELL/EMC hardware and software)

What other advice do I have?


Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
Software Architect with 501-1,000 employees
Real User
I find the density of the product most valuable.

What is our primary use case?

My primary use case for KVM is running multiple VMs and containers on the one node.

What is most valuable?

I find the density of the product most valuable. It is because of kernel same page merging technology (KSM) that is integrated into Linux kernel. That high density makes KVM one of the important players of the virtualization market.

What needs improvement?

In the future release of KVM, I would like to have improved support for Windows guests.

For how long have I used the solution?

More than five years.

What do I think about the stability of the solution?

The stability of this solution is less than other products in the same category. But, it is OK. 

What do I think about the scalability of the solution?

The scalability of the product is really high because of architecture. Since KVM is part of a Linux kernel, it gets a lot of the benefits of its location. It has a nice strategy of memory virtualization, which is also part of the kernel. Kernel location makes possible schemes of a vhost that boosts device performance.

We currently have 300 users of KVM, with about two people as support staff. We do plan to increase usage in the future. So, we will be scaling up in the future.

How are customer service and technical support?

The KVM technical support is really bad. It has a number of empty channels for support. We have tried emails, as well. But, if you are not part of the community, they will not answer your request. 

Which solution did I use previously and why did I switch?

We previously used VMware. 

How was the initial setup?

The initial setup was simple because KVM is used in Linux, so to get it out of the box is a simple task. But, the deployment is not an easy task. It takes a lot of installation suites. You could use a lot of additional products or improvements, like Red Hat virtualization that makes deployment of virtual machines simple. But, out of the box deployment is not that good.

What's my experience with pricing, setup cost, and licensing?

This solution came with the Linux license.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
IT-Leiter (IP) at IN-telegence GmbH
Real User
I like the ability to execute live migrations

What is our primary use case?

Running virtualization clusters with more than 300 VMs.

How has it helped my organization?

The platform changes from hardware to virtualized whenever possible.

What is most valuable?

  • Open source
  • The ability to execute live migrations
  • Linux, a base OS.

What needs improvement?

Management of underlying volumes.

For how long have I used the solution?

Three to five years.
Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
it_user781875 - PeerSpot reviewer
System Architect at a aerospace/defense firm with 10,001+ employees
Real User
Provides a freedom that you do not have with other solutions on the market
Pros and Cons
  • "It is an open ecosystem, and we see there is a benefit in open-source solutions."
  • "We would like to have a software lifecycle solution included in this solution. We can handle the software needed for KVM, but also the software that we provide. A lifecycle component would be very beneficial."

What is our primary use case?

Our primary use for this product is server virtualization.

What is most valuable?

There is a lot of value with an open source solution because you have some freedom of changing how the system behaves and looks because it's open source. You can modify to your requirements which you cannot really do with VMware.

What needs improvement?

The management of the whole system, could be improved. VMware is better on the management tools, for example, Red Hat is when it comes to the KVM.

In addition, we would like to have a software lifecycle solution included in this solution. We can handle the software needed for KVM, but also the software that we provide. A lifecycle component would be very beneficial.

For how long have I used the solution?

More than five years.

What do I think about the stability of the solution?

It is a verty stable solution.

What do I think about the scalability of the solution?

We have over 1000 users using the solution currently. 

How are customer service and technical support?

If I were to rate the technical support on a scale of one to five, I would give it a four. We received good support and there is an on-site presence, as well. 

Which solution did I use previously and why did I switch?

We previously used VMware but switched to KVM because it is an open ecosystem and we see there is a benefit in open source solutions.

How was the initial setup?

It's very straightforward because there are a lot of examples of how to use it. 

What's my experience with pricing, setup cost, and licensing?

It is cheaper than other solutions out there on the market.

Which other solutions did I evaluate?

We also evaluated Red Hat, SUSE, Canonical(Ubuntu), and other Linux providers.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
it_user781875 - PeerSpot reviewer
System Architect at a aerospace/defense firm with 10,001+ employees
Real User
This solution integrates nicely with other soft-open-software components.
Pros and Cons
  • "I think nine out of the ten supercomputers in the world use Linux KVM, so I think that attests to the fact that it is a scalable product."
  • "Technical support is not top-notch."

What is our primary use case?

The main use case is, of course, to run virtual machines. The specific use case is to run virtual network functions (VNFs) and the performance is very good on KVM.

What is most valuable?

A big strength with KVM is that it is an open-source component. It gets improvements from Intel, for example, and the other semiconductors. It can be sized-down to a very small package. It can be used in embedded systems as well, so it has a very good performance and it is suitable from embedded IT to big servers and supercomputers.

This solution integrates nicely with other soft-open-software components.

What needs improvement?

I would like to see a separation, so you could have KVM running in a few cores, and then you could have a real-time operating system running another core, so there is a hybrid environment with real time operating systems and Linux.

For how long have I used the solution?

More than five years.

What do I think about the stability of the solution?

The stability is very good. It has not crashed once since we have been using it. 

What do I think about the scalability of the solution?

I think nine out of the ten supercomputers in the world use Linux KVM, so I think that attests to the fact that it is a scalable product. It scales really well.

How is customer service and technical support?

Technical support is not top-notch.

How was the initial setup?

I think this solution is in need of an easier installation process.

What's my experience with pricing, setup cost, and licensing?

It is cheaper than other competitors like VMware or Hyper-V.

Which other solutions did I evaluate?

We compared KVM vs VMware and did a proof-of-concept, but we decided that KVM was best suited for our needs when it came to device drivers, etc. We also considered Oracle and RedHat.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
System Architect at a tech services company with 11-50 employees
Real User
A very reliable solution which can be used for x86 architecture virtualization with reasonable overhead
Pros and Cons
  • "KVM has a rich options set which can be directly used or via wrappers, such as libvirt."
  • "If you are a Linux desktop user, KVM is the solution to go with if you have to start virtual machines with Linux or other operating systems with almost zero extra configuration needed."
  • "A very reliable solution which can be used for x86 architecture virtualization with reasonable overhead."
  • "The only negative aspect of needing hardware support is a fully functional KVM can be dropped. It would be nice if the support for other platforms, like ARM or Risk, were as good as the x86 one. However, with the democratization of Chromebooks based on these chips and mobile devices, it will not take long for that to happen."

What is our primary use case?

Great support for many types of hardware, disks, memory, RAID controllers, etc.

How has it helped my organization?

In the Linux world, KVM is a very reliable solution which can be used for x86 architecture virtualization with reasonable overhead. Reliable and extensible have a tight integration with Linux security facilities, like SELinux, KVM does the job.

You will unlikely see KVM if you are using a cloud solution because of it is a seamless integration. If instead you are a Linux desktop user, KVM is the solution to go with if you have to start virtual machines with Linux or other operating systems with almost zero extra configuration needed.

KVM has a rich options set which can be directly used or via wrappers, such as libvirt.

What is most valuable?

Our infrastructure is based on KVM and Linux Containers (LXC). We had a lot of VMware legacy, but it was converted to Ubuntu and KVM hypervisor for about the last year. Management and backup is a lot easier with with Ubuntu and KVM, especially combined with ZFS and snapshotting.

What needs improvement?

The support of virtualization in the recent generation of x86 processor is almost a must have, so the only negative aspect of needing hardware support is a fully functional KVM can be dropped. It would be nice if the support for other platforms, like ARM or Risk, were as good as the x86 one. However, with the democratization of Chromebooks based on these chips and mobile devices, it will not take long for that to happen.

For how long have I used the solution?

More than five years.

What's my experience with pricing, setup cost, and licensing?

It is free and can be run from your laptop, if needed, unlike VMware.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
PeerSpot user
Student at Universidade de Brasília at a tech company with 51-200 employees
Consultant
The performance, scalability, and security are valuable.

What is most valuable?

  • Low cost, if not lowest.
  • Great performance and scalability.
  • Security is top-notch.
  • Free.

What needs improvement?

Networking configuration might be annoying depending on how you want to set it up; usually works fine, though.

For how long have I used the solution?

I have used it for one year.

What was my experience with deployment of the solution?

We have not encountered any deployment issues.

What do I think about the stability of the solution?

We have not encountered any stability issues.

What do I think about the scalability of the solution?

We have not encountered any scalability issues.

How are customer service and technical support?

Customer Service:

Well, none.

Technical Support:

Unless you can count open forums?

Which solution did I use previously and why did I switch?

I previously used VMware VM VirtualBox and then Workstation Pro. I switched because VMware is not free.

How was the initial setup?

Initial setup was straightforward.

What about the implementation team?

I implemented it in-house.

What was our ROI?

Since I invested 0 dollars on KVM and just as much time as you would think is worth... you do the math.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
PeerSpot user
Senior Consultant IT Infrastructure at a tech consulting company with 51-200 employees
Consultant
KVM allows me to run virtualized environments for my customer projects and to modify the code as it's open-source, although there were stability issues when running I/O intensive tasks.

What is most valuable?

KVM runs virtualized guests with its own kernel, which is very important to me.

How has it helped my organization?

I mainly use it for customer projects, as KVM allows running virtualized environments for free in a very efficient way. Furthermore, it is an open source solution so modifying the code is possible. One might think that this is never necessary for most projects; however, when a specific customer requested an enhancement of the functionality, I was able to provide that. The customer was very impressed that KVM is such a professional solution although it is free.

Over the years, many customers were happy that they were able to choose between VMware, Xen and another alternative - KVM.

What needs improvement?

Setting KVM up and running it with dozens of parameters can be annoying. However, there is a control interface called Virsh (and also a GUI called virt-manager) which allows running KVM guests with a simple config file.

For how long have I used the solution?

I have been using KVM since 2010, so for fives years in total.

What was my experience with deployment of the solution?

So far, no issues.

What do I think about the stability of the solution?

When running I/O intensive tasks, or having a very high amount of network packages which need to reach the guest(s). However, all issues were under control after tuning the config of the KVM guests.

What do I think about the scalability of the solution?

No issues yet.

How are customer service and technical support?

There is no customer service, only the community. It is a free product, based on open source software. However, one can use RHEV (the enterprise virtualization product from Red Hat), then you will be able to contact the Red Hat support.

Which solution did I use previously and why did I switch?

I used Xen in the past and switched because the customers requested a solution which allows running a guest with its own Kernel. This is also possible with Xen, but not a common use case, though.

How was the initial setup?

The initial setup, when done manually, is complex because you need to be an experienced Linux user or admin, especially as the networking part can be challenging.

What about the implementation team?

I always deploy it on my own.

What's my experience with pricing, setup cost, and licensing?

It is free! Use it and if you need enterprise support, make sure to use RHEV, the virtualization product from Red Hat.

Which other solutions did I evaluate?

No, because in the open source world, there are not many hypervisors which have the same feature set as KVM.

What other advice do I have?

Make sure to gain a lot of knowledge about virtualization and the way KVM works. Then implement it with libvirt and virt-manager because this makes running KVM guests a lot easier.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user

Interesting responses.
QEMU is the underlying technology for KVM, Xen and Virtualbox.
KVM provides accelerators on top of QEMU, and although KVM does not provide the fancy next>next>done GUI of the others, it provides for fine grained tuning, easier cloud orchestration and the widest range of platform/cpu emulations - and windows runs absolutely fine under KVM, even if you want to run a gaming platform, you can passthrough the video adapter, and access the underlying Linux system via ssh, with surprisingly little performance loss.

Arguments around what is best are subjective and use case is the primary relevance.

Large cloud providers work on standards based deployments - working with 10s of thousands of VMs. OpenStack is the prevailing cloud computing deployment architectural standard. libvirt (qemu/KVM on x86) is the only Hypervisor in group 1, which is 100% compatible with standards and fully supported. Group 2 includes Hyper-v, VMWare, Xen, Group 3 includes docker and LXC.

Large and medium enterprise are on the journey of moving to cloud architectures, and inevitably, they will end up with workload sitting on qemu based hypervisor in the future.
Currently, they typically run VMWare, which was largely responsible for the hypervisor revolution, but computing requirements have grown beyond what can be done 'in house' with a small IT team.

The whole IT industry has grown tremendously in the last 20 years. Large portions of company budgets are consumed by IT expenditure, and with this scale, productivity gains are required to keep IT expenditure under control. Higher utilization, thiner server instances, thiner applications, automation, orchestration, co-location, managed services, outsourcing, transformations, the cloud, IoT. Internal IT teams WILL be reduced to being flight deck administrators, with the hardware and software management being handled by someone else. Someone who has the economies of scale, to do things faster, cheaper and better.

Back to Hypervisors...
The main question is, does your 'server' need a head? Do you need to have a desktop environment and management tools installed in the server? Or can the server have these aspects abstracted from the VM and the tasks performed via APIs? (think about windows server core, or linux). This increases efficiencies in many ways.

If you are looking at virtualization, in the context of running an application interface in a contained operating environment, on your local computer, for whatever reason, the reality is that, those requirements are not the requirements of the industy/enterprise for computing infrastructure that the real hypervisors are being built for.

My advice:
If you want to run your own server, with virtualization, use VMWare free version. Or Xen, or QEMU if you like, whatever you are happy with, and meets your requirements - they can all host windows or linux VMs fine.

If you want to use your desktop/laptop with a few guest vms, run VMWare Player or VirtualBox.
If you're a glutton for punishment, install one of the servers first and passthrough the video card at least, if you're using photoshop or playing a modern game, you'll want the video drivers to have direct access to the card.

And if you want to support IT infrastructure in the future, learn to code, because those days of managing your own DC, installing servers, patching, firewalls, hypervisor GUIs, next next next done jobs, wont be around for ever.

See all 13 comments
PeerSpot user
IT Manager at a tech vendor with 51-200 employees
Real User
Top 5
Review about KVM

Valuable Features:

It gives us live VM migrations.

Improvements to My Organization:

It allows us to virtualize our entire IT Infrastructure without any software cost. We only need to spend money on support and deployment.

Use of Solution:

Used since 2009 from version 0.8, so 6 years now.

Deployment Issues:

No.

Stability Issues:

No.

Scalability Issues:

It's scaled for us since version 0.8.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
PeerSpot user
Business process Advisor for RTP at a energy/utilities company with 10,001+ employees
Real User
I had lots of issue with it.

I have used KVM with centos 7. Unfortunately, I had lots of issue with it. First of all, I wanted all the VMs to share the same network. I had to modify the centos network interface files myself. I had to do it with every single VM. 

At some point it created lots of issue in the module firewalld which also act as the nat to connect the VM with the physical interface. I could read "command failed" for rules of a VM that was already deleted in KVM. 

Then, I had issues with virsh the command line of KVM. Among other things, it exports and imports VM. I wanted to move a Virtual Machines from kvm on centos bare metal server to kvm on debian bare metal server and I discovered that in order to do so, I had to modify the XML configuration inside the VM file. 

I have also been unable to clone VMs meaning they when i tried to run some VMs after cloning, they refused to start. I have also crashed the Centos host. At that point, I have decided to stop and move to my old friend Vmware workstation on Linux. I didn't have to modify any interface files and I could use a "bridge" mode by choosing it in the options so that all my VM were on the same network. Ok, Vmware workstation isn't a bare metal hypervisor but it is reliable. 

By the way, I prefer to spend time on developing stuff than spending my time setting up KVM or learning the commands of virsh to do basic stuff with it. 

On the internet, many geeks pinpoint the performance of KVM. It is true but it is futile issue as compared to issues related to a production environment. 

I am sorry to say that online propaganda made believe that KVM is a mature product that should be considered for production. I think KVM may be good for a lab where the VMs aren't critical.

Now, when I see Web hosting providers who run the Vps on top of KVM, I don't see them the same way. 

This made me aware of the issue related to the Type 1 hypervisor. Since a type 1 is a bare metal type hypervisor, it deals with masquerading (NAT), security, kernel, memory, data IO... Because of that, every module has to extremely stable and bug free. As I said before, I have been able to crash a centos 7 bare metal host (meaning it didn't reboot) without tweaking any packages or renaming any files. Just by doing heavy normal maintenance over Virtual machines. (Deleting, adding, cloning, changing virtual hardware, changing network data, Changing name...). 

On the other hand Vmware workstation is a Type 2 hypervisor meaning that this software is going to interact with the host without really modifying it. I did the same things as with KVM without any crash.

I am a MCSE and i have started "hypervising" with Ms Hyper V which is way better than KVM. As i am writing this, I think about all the good things, people write online about KVM. It makes believe that KVM is as good as Hyper V. However, it is not close to the truth. Hyper V is more stable. Its files are more portable. The migration features are robust. More importantly, it uses hardware better than Linux based KVM.

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user
it_user175725 - PeerSpot reviewer
it_user175725Solution Engineer at a engineering company with 51-200 employees
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Helpful info for evaluating of use.

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Tech Support Staff with 51-200 employees
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Possibility of using KVM Virtualization in Hosting

Virtualization has made a lot of progress during the last decade, primarily due to the development of myriad open source virtual machine hypervisors. This progress has almost diminished the barriers between operating systems. There are mainly two types of virtualizations; Software Virtualiztion and Hardware Virtualization. Up until recently, the focus always has been on software­emulated virtualization.


KVM

KVM is short for Kernel­based Virtual Machine and makes use of hardware virtualization, i.e., you need a CPU that supports hardware virtualization, e.g. Intel VT or AMD­V. Connsidering the time line of virtualization techniques, KVM is a relative newcomer. Several incumbent open source methods exist today, such as Xen, Bochs, UML, Linux VServer, and coLinux, but KVM is receiving a surprising amount of exposure now. KVM is a unique hypervisor. It consists of a loadable kernel module that provides the core virtualization infrastructure and a processor specific module. Using KVM virtualization, one can run multiple virtual machines running unmodified Linux or Windows images. Each virtual machine has private virtualized hardware: a network card, disk, graphics adapter, etc. The kernel component of KVM is included in mainline Linux. KVM is a relatively new and simple, yet powerful, virtualization engine, which has found its way into the Linux kernel, giving the Linux kernel native virtualization capabilities. Because KVM uses hardware­based virtualization, it does not require modified guest operating systems, and thus, it can support any platform from within Linux, given that it is deployed on a supported processor.


Advantages of KVM Virtualization


• High Security
• performance and scalability
• Adequate for most cloud deployments
• Simple type­2 hypervisor
• Easy to setup
• Open source software
• Run multiple virtual machines running unmodified Linux or Windows images.
• Each virtual machine will have private virtualized hardware: a network card, disk, graphics adapter, etc
• More flexible compared to other virtualiztion technologies.
• KVM is the best Linux kernel­integrated hypervisor technology.


A typical KVM installation consists of the following components:


• A device driver for managing the virtualization hardware; this driver exposes its capabilities via a character device /dev/kvm.
• A user­space component for emulating PC hardware; currently, this is handled in the user space and is a lightly modified QEMU process.
• The I/O model is directly derived from QEMU's, with support for copy­on­write disk images and other QEMU features.


How to check System Compatibility ?

First, you need a processor that supports virtualization. For a more detailed list, you can refer xensource wiki. You can tell whether your system supports virtualization by looking at /proc/cpuinfo. This file specifies whether the vmx (Intel) or svm (AMD) extensions are supported. A wide variety of guest operating systems work with KVM hypervisor, including many flavours of Linux, BSD, Solaris, and Windows Operating Systems. A modified version of Qemu can use KVM to run Mac OS X.


KVM vs Existing Hypervisors :

In many ways, VMware is a ground­breaking technology. VMware manages to fully virtualize the notoriously complex x86 architecture using software techniques only, and to achieve very good performance and stability. As a result, VMware is a very large and complex piece of software. KVM, on the other hand, relies on the new hardware virtualization technologies that have appeared recently. As such, it is very small (about 10,000 lines) and relatively simple. Another big difference is that VMware is proprietary, while KVM is open source. KVM will, in the long run, greatly benefit from taking advantage of advancements in the kernel, without developers having to re­invent them, as is the case with Xen.

Xen is a fairly large project, providing both paravirtualization and full virtualization. It is designed as a standalone kernel, which only requires Linux to perform I/O. This makes it rather large, as it has its own scheduler, memory manager, timer handling and machine initialization.

KVM, in contrast, uses the standard Linux scheduler, memory management and other services. This allows the KVM developers to concentrate on virtualization, building on the core kernel instead of replacing it.

QEMU is a user­space emulator. It is a fairly amazing project, emulating a variety of guest processors on several host processors, with fairly decent performance. However, the user­space architecture does not allow it to approach native speeds without a kernel accelerator. KVM recognizes the utility of QEMU by using it for I/O hardware emulation.


KVM vs Existing Hypervisors :

KVM

KVM

KVM


Limitations of KVM virtualiation:


• Currently, KVM supports only Intel and AMD virtualization, whereas Xen supports IBM
• PowerPC and Itanium as well. SMP support for hosts is lacking in the current release.
• Performance tuning.


However, KVM already is further ahead than other hypervisor solutions in some areas and surely will catch up in other areas in the future. KVM is the best technology going forward for open source virtualization.

With the introduction of KVM into the Linux kernel, future Linux distributions will have built­in support for virtualization, giving them an edge over other operating systems. There will be no need for any dual­boot installation in the future, because all the applications you require could be run directly from the Linux desktop. KVM is just one more of the many existing open­source hypervisors, reaffirming that open source has been instrumental to the progress of virtualization technology.

The above is a very rough outline of KVM Virtualization, and if you have any questions, we would be happy to talk to you! :)

Disclosure: I am a real user, and this review is based on my own experience and opinions.
PeerSpot user

The CLI on ESXi only can be executed from a windows PC (if you use the free ESXi). The other option is very, very expensive compared with KVM. This is a major reason why I prefer KVM over VMWare. The support of scripting in ESXi free is very limited, in the other hand, KVM works in a normal linux distribution, so, you have all the power of scripting to do what ever you like.

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Buyer's Guide
Download our free Server Virtualization Software Report and find out what your peers are saying about KVM, Oracle, Microsoft, and more!
Updated: September 2022
Buyer's Guide
Download our free Server Virtualization Software Report and find out what your peers are saying about KVM, Oracle, Microsoft, and more!