Xen,vmware the principles of virtualization technologies such as ESXI,HYPER-V and KVM

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Xen,vmware the principles of virtualization technologies such as ESXI,HYPER-V and KVMApril 03, 2018 13:51:55 read: 936

XEN compared to VMware esxi,hyper-v and KVM features:

XEN has simplified virtual mode, does not need device driver, can ensure that each virtual user system is independent of each other, relying on service domains to complete some functions;

VMware ESXI is similar to XEN and includes basic elements such as device drivers and management stacks, and hardware support relies on VMware-created drivers;

Hyper-V is a modification based on the XEN management stack;

KVM is different from XEN, and KVM is based on the Linux kernel as a management tool.

Architecture of virtual machines

XEN Architecture

Figure 3. XEN architecture Diagram

A XEN virtual machine environment consists mainly of the following components:

XEN Hypervisor;

Domain 0--domain Management and Control (XEN dm&c);

Domain u Guest (Dom u)

4 shows the relationships in addition to the parts:

Figure 4. Xen three-part relationship Diagram

XEN Hypervisor:

XEN Hypervisor is a software description layer between the operating system and the hardware. It is responsible for CPU scheduling and memory allocation between the various virtual machines. The XEN Hypervisor not only abstracts the hardware of the virtual machine, but also controls the execution of each virtual machine. XEN Hypervisor does not handle networks, storage devices, video, and other I/O.

Domain 0:

Domain 0 is a modified Linux kernel, the only virtual machine running on Xen Hypervisor that has access to physical I/O resources while interacting with other virtual machines running on the system. Domain 0 needs to be started before other domain launches.

Domain U:

All para-virtualized (paravirtualized) VMs running on Xen Hypervisor are referred to as "Domain U PV Guests", which runs a modified kernel operating system, such as Linux, Solaris, FreeBSD, and other UNIX operating system. All fully virtualized virtual machines are known as "Domain U HVM Guests", which run on operating systems that do not have to modify the kernel, such as Windows.

2.hyper-v Architecture

Figure 5. Hyper-V architecture diagram

hyper-v is a system hypervisor virtualization technology proposed by Microsoft, which takes into account the requirements of security and performance by using microkernel architecture. The Hyper-V Hypervisor runs at the highest level of privilege, which Microsoft calls Ring-1 (and Intel calls it root mode), while the OS kernel and drivers of the VM run in Ring 0, and the application runs under Ring 3, which is not Complex BT (binary privileged instruction translation) technology is required to further enhance security. From the architecture, Hyper-V only "hardware-hyper-v-virtual machine" Three layer, itself very small, simple code, and does not contain any third-party drivers, so safe and reliable, efficient execution, can make full use of hardware resources, so that virtual machine system performance closer to real system performance.

HYPER-V supports partition-level isolation. A partition is a logical isolation unit that is supported by the hypervisor and is executed by the operating system. Microsoft hypervisor must have at least one parent/root partition that is used to run the 64-bit version of the Windows Server 2008 operating system. The virtualization stack runs in the parent partition and provides direct access to the hardware device. The root partition then creates sub-partitions that are used to host the guest operating system. The root partition uses virtualization to invoke the Application programming interface (API) to create sub-partitions.

Partitioning does not have access to the physical processor, nor can it handle processor interrupts. Instead, they have a virtual view of the processor and run on the virtual memory address area dedicated to each guest partition. The hypervisor is responsible for handling processor interrupts and redirecting them to the appropriate partitions. Hyper-V can also leverage hardware acceleration through the input and output memory management unit (IOMMU) to accelerate address translation between each guest virtual address space. The IOMMU runs independently of the CPU-used memory management hardware and is used to remap the physical memory address to the address used by the child partition. From the system's structure diagram, we can see that Hyper-V is similar to Xen's architecture.

Figure 6. Vmware ESXI architecture Diagram

We can see that management tools are also embedded directly into ESXi VmKernel, and no separate management tools are differentiated from Xen.

Figure 7. KVM architecture Diagram

KVM is a unique hypervisor that, by implementing KVM as a kernel module, can simplify management and improve performance in a virtualized environment as a loadable module for the Linux kernel integration Manager. In this mode, each virtual machine is a regular Linux process that is dispatched through the Linux scheduler.

With the architecture diagram of the four virtual machines above, we can see their location throughout the system and the difference between them.

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How XEN Works

We have a simple description of the Xen architecture, and we know that Xen is mainly made up of Xen Hypervisor,domain0,domainu three parts. Here's how Xen works by communicating with domain 0 and interacting with the three parts.

We have already mentioned that Domain U is divided into PV customer System and HVM Customer System, we first discuss the PV customer system, that is, the semi-virtualized operating system working principle.

First we need to know that there are two driver network backend Driver and Block backend Driver in domain 0, which are used to process networks and local disk requests from domain U, respectively. Because Xen Hypervisor does not support network and disk requests, a PV (semi-virtualized) customer system must communicate with Xen Hypervisor, Domain 0 to implement network and disk requests. As the Xen documentation has explored how the PV customer System writes a data to a local hard disk, let's discuss how the PV customer System sends a data to the network. The first thing we need to know is that domain U PV Guest also includes two drivers "PV network Driver" and "PV Block Driver", which are also used for sending network and local disk requests, which are two in domain 0. A driver is a relative response.

When a PV client system's network device driver receives a request to send data and sends data via Xen Hypervisor to a local network device (a device such as a network card), this network device is shared with Domain 0. There is an event channel between domains 0 and domain U that asynchronously communicates inter-domain interrupts through the channel. Domain 0 will receive an interrupt from the Xen Hypervisor, triggering the PV network backend Driver access to the above networked devices, reading the data from the PV client system, and sending the data.

Figure 8. Domain 0 and domain U PV Guest communication

Above we have analyzed the PV Customer System working principle, below we briefly introduce the HVM Customer system working principle.

Since there is no PV driver mentioned above in a HVM Guests virtual machine, Xen initiates a daemon in Domain 0 for each HVM guest QEMU-DM process network and disk requests from the customer's system, so when a HVM guest When there is a corresponding network and I/O request, it interacts directly with the DOMAIN0 and its corresponding QEMU-DM, which is ultimately achieved through Domain 0 to access the network device or disk. See 9:

Figure 9. Domain 0 and domain U HVM Guest communication


Through this part of the presentation, we have learned about the current development and status of Xen, and we have detailed instructions on how to install Xen under FEDORA13 and some basic operations under Xen, and then we discuss the Xen and VMware esxi,hyper-v and KVM At the same point, finally we explain how Xen works with examples. In the second part of this series, we will explain how to build a Xen development environment, the related technologies that need to be developed under Xen, and how to use XENAPI for development under Xen, and finally demonstrate it through an example.

Source: https://www.server110.com/xen/201404/10378.html


Xen,vmware the principles of virtualization technologies such as ESXI,HYPER-V and KVM

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