KVM VPS vs. OpenVZ VPS

A KVM VPS is better than an OpenVZ VPS.

KVM VPS

Enterprise Grade KVM Managed VPS

KVM offers enterprise grade full virtualization. Every KVM VPS runs on its own dedicated kernel and file system. Hence it is not affected by another abusive VPS on the same hardware. Since it runs on its own dedicated resources, a KVM VPS offers high uptime and performance. tmzVPS offers managed KVM SSD VPS plans from $30/month and unmanaged KVM SSD VPS plans from $10/month.

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Budget OpenVZ Managed VPS

OpenVZ is not a full virtualization technology. You still get full root access however an OpenVZ VPS runs on a shared kernel and file system. Since the resources are shared, an OpenVZ VPS may be affected by an abusive neighbor on the same hardware. Further, an OpenVZ VPS offers inferior performance and lesser uptime than a KVM VPS.


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Managed VPS: KVM VPS vs. OpenVZ VPS

Managed VPS KVM VPS OpenVZ VPS
SSD Storage
Virtualization KVM OpenVZ
Managed VPS
Performance
Uptime
Kernel Dedicated Shared
File system Dedicated Shared
Security
KVM Managed VPS OpenVZ Managed VPS

Understanding KVM vs. OpenVZ Virtualization

The root of the difference between KVM and OpenVZ is in how each virtual machine is virtualized. KVM offers full virtualization. That means that each KVM VPS is a totally independent virtual server. The underlying host provides a set of virtual hardware that an OS is installed on top of. That leads to some of the major advantages of KVM. First, any OS that can run on virtualized hardware can be run on a KVM VPS. It also means that there are no restrictions on the version of the OS that will work - it isn't dependent at all on the host node's OS. You can run an older kernel, newer kernel, same version kernel.

It also means that nothing happening inside the VPS is affected by, or affects, other servers running on the node. You can choose any sort of configuration options or software without impacting other people, and vice versa. The VPS is also isolated from software vulnerabilities in other nodes. If someone managed to break into a VPS, there is no possible access to anything outside the VPS.

OpenVZ uses containerized virutalization. In many ways, it appears to be the same as KVM virtualization, and for the basics it's quite similar. However, unlike full virtualization it does not provide a totally independent virtual machine. As such, each individual VM is limited in the choice of operating systems and the degree to which they can be customized. One commonly encountered limit is that a VM cannot run a newer kernel than the host node is using. This is because the kernel code is actually shared between all of the VMs. This provides some added efficiency, in that any one VM does not need to load their own version of the kernel. Saving resources with shared kernels means that VMs get to use more of their allocated resources on user software.


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Similarities between KVM and OpenVZ

There are many things that are the same or at least similar between these two virtualization solutions. In particular, the experience of USING a VM based on each will be nearly the same.

• Both allow various different operating systems to be installed on a VM
• Both allow remotely accessing the VM via SSH and provide the user experience of being remotely logged into a physical server
• Both allow installing nearly any software that is compatible with the OS installed in the VM. There maybe be some limitations in OpenVZ based on the available kernel running on the host (ie, a KVM VM could have the kernel upgraded to accomodate specific software requirements while OpenVZ cannot)
• The server can be rebooted, stopped, or started in either case, the same as a physical box
• Limits on resources can be specified for each. They both will present a specific amount of disk, RAM, and available processing power. It should be noted that given the same amount of RAM assigned to the VM, an OpenVZ instance will have more available to the user as it doesn't need to dedicated RAM to shared code, like the kernel.
• Most of the experience inside the VPS will be indistinguishable between the two, or to a physical server. Software, users, settings, security, etc, can all be customized within the VM.
• Performance and reliability - both operating environments can deliver outstanding performance and uptime to the end user. As long as the hardware on the host node is high quality and sufficient for the provisioned VMs, speedy performance and always-on reliability should be the norm.

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