[linuxkernelnewbies] IBM: Virtual systems overview

[peter teoh]

http://publib.boulder.ibm.com/infocenter/eserver/v1r2/index.jsp?topic=/eicay/eicayvservers.htm Virtual systems overview System virtualization enables you to consolidate systems, workloads, and operating environments, optimize resource use, and improve IT flexibility and responsiveness. System virtualization creates many virtual systems within a single physical system. Virtual systems are independent operating environments that use virtual resources. System virtualization can be approached through hardware partitioning or hypervisor technology. Hardware partitioning subdivides a physical server into fractions, each of which can run an operating system. These fractions are typically created with coarse units of allocation, such as whole processors or physical boards. This type of virtualization allows for hardware consolidation, but does not have the full benefits of resource sharing and emulation offered by hypervisors. Hypervisors use a thin layer of code in software or firmware to achieve fine-grained, dynamic resource sharing. Because hypervisors provide the greatest level of flexibility in how virtual resources are defined and managed, they are the primary technology of choice for system virtualization. There are two types of hypervisors. Type 1 hypervisors run directly on the system hardware. The following figure shows one physical system with a type 1 hypervisor running directly on the system hardware, and three virtual systems using virtual resources provided by the hypervisor. Type 2 hypervisors run on a host operating system that provides virtualization services, such as I/O device support and memory management. The following figure shows one physical system with a type 2 hypervisor running on a host operating system and three virtual systems using the virtual resources provided by the hypervisor. Type 1 hypervisors are typically the preferred approach because they can achieve higher virtualization efficiency by dealing directly with the hardware. Type 1 hypervisors provide higher performance efficiency, availability, and security than type 2 hypervisors. Type 2 hypervisors are used mainly on client systems where efficiency is less critical. Type 2 hypervisors are also used mainly on systems where support for a broad range of I/O devices is important and can be provided by the host operating system. IBM® supports at least one hypervisor for each IBM system. The following table lists IBM systems and the hypervisors that they support. Table 1. IBM systems and supported hypervisors Hypervisor Hypervisor type IBM system that runs hypervisor Microsoft® Virtual Server Type 2 System x™ and BladeCenter® POWER5™ Type 1 System i™ and System p™ Processor Resource/System Manager Type 1 System z™ VMware ESX Server Type 1 System x and BladeCenter VMware GSX Server Type 2 System x and BladeCenter VMware Server Type 2 System x and BladeCenter Xen Type 1 System x and BladeCenter z/VM® Type 1 System z System virtualization yields the following benefits: Consolidate systems, workloads, and operating environments: Multiple workloads and operating systems can be combined onto one physical server, reducing the costs of hardware and operations. New versions of software can be tested on the hardware that they will later use in production mode without affecting production workloads. Virtual systems can be used as low-cost test systems without jeopardizing production workloads. Multiple operating system types and releases can run on a single system. Each virtual system can run the operating system that best matches its application or user requirements. Optimize resource use: Hypervisors can achieve high resource use by dynamically assigning virtual resources (such as processors and memory) to physical resources through mechanisms such as dispatching and paging. The virtual resources that they provide can exceed the physical system resources in quantity and functionality. System virtualization enables the dynamic sharing of physical resources and resource pools. This results in higher resource use, especially for variable workloads whose average needs are much less than an entire dedicated resource. Different workloads tend to show peak resource use at different times of the day and week, so implementing multiple workloads in the same physical server can improve system use, price, and performance. Improve IT flexibility and responsiveness: Service providers can create one virtual system or clone many virtual systems on demand, achieving dynamic resource provisioning. Virtual systems with variable resources enable the manual or automated management of workload resources. Parent topic: Virtualization overview Related information Virtualizing a system Managing a virtual system   -- To unsubscribe, reply using "remove me" as the subject.