1. OpenVZ Architecture Servers
OpenVZ is an operating-system-level virtualization technology based on the Linux kernel and operating system. OpenVZ allows a physical server to run multiple operating systems, known as Virtual Private Servers (VPS) or Virtual Environments (VE).
OpenVZ is OS-level virtualization, acting as a layer of application on top of the underlying operating system. This means it is easy to understand, has low overhead, and generally offers better performance. This architecture allows direct calls to the host machine’s kernel to simulate and spawn child servers. However, after virtualization, the performance loss compared to the host machine is only about 1-3%.
Because of this advantage, OpenVZ servers can be “oversold.” “Overselling” means that while a typical server could be split into 100 sub-servers to sell to 100 people, due to OpenVZ’s advantage, it can be split into 200 sub-servers to sell to 200 people. This is overselling.
Advantages: The types sold on the market now feature huge memory and strong CPUs. There are many sellers, making them highly comparable with excellent price-performance ratios.
Disadvantages:
1. Precisely because of overselling, what is an advantage for merchants becomes a disadvantage for buyers. The associated CPU is also excessively partitioned, causing its actual performance to be less than one-tenth of what is advertised. As for memory, OpenVZ technology essentially has no dedicated allocation; everything is shared. If others use more, you get less. The biggest drawback of this technology is that when memory runs out, the server simply crashes.
2. It is difficult to implement acceleration. Since OpenVZ’s virtualization architecture is not sufficiently thorough, acceleration is hard to achieve.
Example: The low-cost VPS pioneer BandwagonHost primarily uses this architecture. Early circumvention servers were often set up on BandwagonHost. Later, BandwagonHost noticed a large number of these users and added a VPN function to the server’s backend control panel.
2. Xen Architecture Servers
Xen is an open-source virtual machine monitor developed by the University of Cambridge. It aims to run up to 100 fully-featured operating systems on a single computer. Operating systems must be explicitly modified (“ported”) to run on Xen (while providing compatibility for user applications). This allows Xen to achieve high-performance virtualization without special hardware support (Xen HVM requires CPU virtualization features).
Xen is a paravirtualization technology. It is not a true virtual machine but rather runs an instance of a kernel, allowing free loading of kernel modules, virtual memory, and I/O. It is stable and predictable. It is divided into Xen PV and Xen HVM; the difference is that PV only supports Linux, while HVM supports Windows systems.
Advantages:
1. Memory is dedicated; although small, the allocation is guaranteed. The partial virtualization technology ensures that even if overselling occurs, it won’t be too extreme.
2. Acceleration can be implemented.
Disadvantages: Compared to OpenVZ at the same price point, memory is smaller, disk space is smaller, and bandwidth is lower. Because overselling is not feasible, sellers have to reduce these three basic configurations to make a profit, leading to uneven supplier quality.
3. KVM Architecture Servers
KVM stands for Kernel Virtual Module. KVM is the latest virtualization technology introduced in Red Hat Enterprise Linux 5.4. KVM is a virtualization project built into the Linux kernel. It is still in its early stages and not widely known yet. However, with Red Hat’s increasing promotion efforts, it is believed that KVM will gradually dominate the market in the near future.
Its feature is the ability to virtualize different CPUs. For example, on an x86 CPU, it can virtualize a Power CPU and use it to compile programs that run on Power. KVM uses parts of QEMU, slightly modified to become the userspace tool for controlling KVM. Therefore, you will see that the official KVM download consists of two main parts in three files: the KVM module, the QEMU tool, and a combined package of the two. This means you can upgrade just the KVM module or just the QEMU tool independently. This is the relationship between KVM and QEMU.
KVM-based VPS tends to be more expensive, but KVM architecture VPS is relatively more flexible compared to other architectures.
Advantages:
1. Similar to Xen, but better in that KVM is fully virtualized, so there is no distinction between PV and HVM. All KVM-type virtualization technologies can install various Linux distributions and various Windows distributions. Regardless of whether the provider’s homepage states Windows support, as long as your configuration meets Windows requirements, you can definitely install it; it’s just a matter of method.
2. It can achieve perfect acceleration.
Disadvantages:
1. KVM-based VPS is more expensive.
2. Precisely because KVM allows installing any type of operating system, some tinkerers even install Windows 2003 on a 128MB machine. The result is that all KVM neighbors have to depend on the behavior of the users around them. Let’s put it this way: if there are just 5 or 6 such tinkerers under a single node, sorry, but your hard disk performance will basically be terrible.
Finally, here is a script to check the server architecture:
wget -N –no-check-certificate https://raw.githubusercontent.com/91yun/code/master/vm_check.sh &&