SUSE Linux Enterprise Serve Virtualization with Xen

SUSE Linux Enterprise Server

Virtualization with Xen

 

 

1.1. Basic Components

 

The basic components of a Xen-based virtualization environment are the Xen hypervisor, the Domain0, any number of other VM Guests, and the tools, commands, and configuration files that let you manage virtualization. Collectively, the physical computer running all these components is referred to as a VM Host Server because together these components form a platform for hosting virtual machines.

The Xen Hypervisor

The Xen hypervisor, sometimes referred to generically as a virtual machine monitor, is an open-source software program that coordinates the low-level interaction between virtual machines and physical hardware.

The Domain0

The virtual machine host environment, also referred to as Domain0 or controlling domain, is comprised of several components, such as:

• The SUSE Linux operating system, which gives the administrator a graphical and command line environment to manage the virtual machine host components and its virtual machines.
  

  The term “Domain0” refers to a special domain that provides the management environment. This may be run either in graphical or in command line mode.

• The xend daemon (xend), which stores configuration information about each virtual machine and controls how virtual machines are created and managed.
• A modified version of QEMU, which is an open-source software program that emulates a full computer system, including a processor and various peripherals. It provides the ability to host operating systems in full virtualization mode.

Xen-Based Virtual Machines

A Xen-based virtual machine, also referred to as a VM Guest or DomU consists of the following components:

• At least one virtual disk that contains a bootable operating system. The virtual disk can be based on a file, partition, volume, or other type of block device.
• Virtual machine configuration information, which can be modified by exporting a text-based configuration file from xend or through Virtual Machine Manager.
• A number of network devices, connected to the virtual network provided by the controlling domain.

Management Tools, Commands, and Configuration Files

There is a combination of GUI tools, commands, and configuration files to help you manage and customize your virtualization environment.

1.2. Understanding Virtualization Modes¶

Guest operating systems are hosted on virtual machines in either full virtualization mode or paravirtual mode. Each virtualization mode has advantages and disadvantages.

• Full virtualization mode lets virtual machines run unmodified operating systems, such as Windows* Server 2003 and Windows XP, but requires the computer running as the VM Host Server to support hardware-assisted virtualization technology, such as AMD* Virtualization or Intel* Virtualization Technology.
  Some guest operating systems hosted in full virtualization mode, can be configured to run the Novell* Virtual Machine Drivers instead of drivers originating from the operating system. Running virtual machine drivers improves performance dramatically on guest operating systems, such as Windows XP and Windows Server 2003. For more information, see Chapter 13, Virtual Machine Drivers.
• Paravirtual mode does not require the host computer to support hardware-assisted virtualization technology, but does require the guest operating system to be modified for the virtualization environment. Typically, operating systems running in paravirtual mode enjoy better performance than those requiring full virtualization mode.
  Operating systems currently modified to run in paravirtual mode are referred to as paravirtualized operating systems and include SUSE Linux Enterprise Server 11 and NetWare® 6.5 SP8.

1.3. Xen Virtualization Architecture¶

The following graphic depicts a virtual machine host with four virtual machines. The Xen hypervisor is shown as running directly on the physical hardware platform. Note, that the controlling domain is also just a virtual machine, although it has several additional management tasks compared to all other virtual machines.

Figure 1.1. Virtualization Architecture¶

On the left, the virtual machine host’s Domain0 is shown running the SUSE Linux operating system. The two virtual machines shown in the middle are running paravirtualized operating systems. The virtual machine on the right shows a fully virtual machine running an unmodified operating system, such as Windows Server 2003 or Windows XP.

1.4. The Virtual Machine Host¶

After you install the virtualization components and reboot the computer, the GRUB boot loader menu displays a Xen menu option. Selecting the Xen menu option loads the Xen hypervisor and starts the Domain0 running the SUSE Linux operating system.
Running on Domain0, the SUSE Linux operating system displays the installed text console or desktop environment, such as GNOME or KDE. The terminals of VM Guest systems are displayed in their own window inside the controlling Domain0 when opened.

Figure 1.2. Desktop Showing Virtual Machine Manager and Virtual Machines¶

1.5. Supported Virtualization Limits¶

Although Xen may operate well with extended parameters, its operation on SUSE Linux Enterprise Server 11 SP2 is supported only within the limits shown in the tables below. Note that PV stands for paravirtualization, while FV stands for full virtualization.

Xen 32-bit Hypervisor Removed

Because vast majority of our customers already moved to 64-bit Xen hypervisors, we decided to focus the development and testing efforts to support 64-bit Xen hypervisors only. Therefore the 32-bit flavor of the Xen hypervisor was removed from SUSE Linux Enterprise Server 11 SP2. This means that only 64-bit x86-based VM hosts are supported. This does not affect VM guests - both 32-bit and 64-bit flavors are supported.

	Minimal Required Memory
Please consider that the VM host server needs at least 512 MB of memory. If you are adding virtual machines to it, you must add additional memory to this base requirement.

Table 1.1. Supported Limits per Virtual Machine

VM Limits	Xen 4.1
Max. virtual CPUs	32 PV, 16 FV
Max. memory	256 GB
Max. virtual network devices	8
Max. virtual block devices	100 PV, 4 FV (100 with PV drivers)

Table 1.2. Supported Limits for Virtual Host Server

VHS Limits	Xen 4.1
Max. physical CPUs	64
Max. dom0 virtual CPUs	64
Max. physical memory	500 GB (dom0), 2 TB (Xen)
Max. block devices	12,000 SCSI logical units
Max. iSCSI devices	128
Max. network cards	8
Max. virtual machines per CPU core	8
Max. virtual machines per VM host	64
Max. virtual devices per VM host	2,048
Max. virtual network cards	64 across all virtual machines in the system

1.6. Supported VM Guests¶

This section lists the support status for various guest operating systems virtualized on top of SUSE Linux Enterprise Server 11 SP2. All guest operating systems are supported both fully-virtualized and paravirtualized with two exceptions: Windows, which is only supported fully-virtualized, and OES and Netware operating systems which are only supported paravirtualized. All guest operating systems are supported both in 32-bit and 64-bit flavors, unless stated otherwise (see Netware).
The following guest operating systems are fully supported:

• SUSE Linux Enterprise Server 10 SP4
• SUSE Linux Enterprise Server 11 SP1
• SUSE Linux Enterprise Server 11 SP2
• Open Enterprise Server 2 SP3
• Netware 6.5 SP8 (32-bit only)
• Windows 2003 SP2+
• Windows 2008 SP2+
• Windows 2008 R2+

The following guest operating systems are supported as a technology preview (fixes if reasonable):

• SUSE Linux Enterprise Desktop 11 SP2

The following guest operating systems are supported on a best-effort basis (fixes if reasonable):

• Windows XP SP3+
• Windows Vista SP2+
• Windows 7 SP1+
• RedHat Enterprise Linux 4.8+
• RedHat Enterprise Linux 5.5+
• RedHat Enterprise Linux 6.0+

The following guest operating systems will be fully supported when released:

• Open Enterprise Server 11

1.7. Supported VM Hosts¶

This section lists the support status of SUSE Linux Enterprise Server 11 SP2 running as a guest on top of various virtualization hosts (hypervisors). Both 32-bit and 64-bit versions are supported. There is full support for SUSE host operating (for both, guest and host). There is full support for 3rd party host operating (for guest).
The following SUSE host operating systems are supported:

• SUSE Linux Enterprise Server 10 SP4
• SUSE Linux Enterprise Server 11 SP 1
• SUSE Linux Enterprise Server 11 SP 2

The following 3rd party host operating systems are supported:

• VMware ESX 4.1
• VMware ESXi 4.1
• Windows 2008 SP2+
• Windows 2008 R2+
• Citrix XenServer 5.6 FP1

The following SUSE and 3rd party host operating systems will be supported when released:

• VMware ESX 4.2
• VMware ESXi 4.2
• Citrix XenServer 5.7
• Windows 2008 future service packs