1.2 SYSTEM VIRTUALIZATION MODELS using software toencode code128 for web,windows application GS1 Bar Codes Center also be partitionable s Software Code 128 o that a failure there affects only the one partition using that component. This isolation scheme is shown in Figure 1.17.

. Figure 1.17 Failure Isolation of Hardware Partitions 1.2.1.

2 Operating Syste Software code 128 code set c m Separate hardware requires a distinct copy of an operating system for each partition. This arrangement reinforces the separation of the partitions and maintains the bene ts, and effort, of per-partition OS maintenance, such as OS installation and patching. To maximize partition independence, a failure in one OS instance must be prevented from affecting another partition.

Also, specialized software (such as HA clustering) that links two partitions must prevent one failure from affecting both partitions. Some implementations in the industry achieve this level of independence more effectively than others. 1.

2.1.3 Flexibility and Granularity of Resource Con guration Most hard-partitioning systems allow the partitions to be different sizes.

A partition can usually be resized. With some types, this operation requires stopping all software, including the operating system, that was using the resources being recon gured. Changing the sizes of two partitions can be viewed as moving the barrier between them, as depicted in Figure 1.

18 on the next page. Most of these systems are large-scale systems (more than eight CPU sockets per system) and contain multiple CPU sockets on each circuit board. If such a system is con gured with multiple partitions per CPU board, a hardware failure on that CPU board can cause multiple partitions to fail.

CPU failures affect only the partition that was using that CPU. For that reason, where failure isolation is the most important consideration, only one partition should be con gured per CPU board. In contrast, if partition density is the most important consideration, multiple partitions per CPU board will be an important feature.

. 1 . Introduction to Virtualization Figure 1.18 Dynamic Reallocation of Hardware Resources 1.2.1.

4 Scalability Two Software barcode code 128 related types of scalability exist in the context of system virtualization: guest scalability and per-VE performance scalability. Guest scalability is the number of VEs that can run on the system without signi cantly interfering with one another. Hard partitions are limited by the number of CPUs or CPU boards in the system, but can also be limited by other hardware factors.

For some of these systems, only 2 partitions can be con gured for each system. For others, as many as 24 partitions can reside in the system. Because these systems are generally intended to perform well with dozens of CPUs in a single system image, they usually run large workloads on a small number of partitions.

Their value derives from their combination of resource exibility, failure isolation, and per-VE performance scalability. Because hard partitioning does not require an extra layer of software, there should be no performance overhead inherent in this type of virtualization. Applications will run with the same performance as in a nonpartitioned system with the same hardware.


5 Partition Management Hardware isolation requires specialized hardware. This requirement usually includes components that aid in the management of the partitions, including the con guration of hardware resources into those partitions. These components may also assist in the installation, basic management, and health monitoring of the OS instances running on the partitions.

Specialized ASICs control data paths and enforce partition isolation.. 1.2 SYSTEM VIRTUALIZATION MODELS 1.2.1.

6 Relative Streng Code 128 Code Set A for None ths of Hardware Partitions Hardware partitions offer the best isolation in the virtualization spectrum. Whenever isolation is the most important factor, hardware partitions should be considered. Partitions are the only virtualization method that achieves native performance and zero performance variability.

Whether the workload is run in an eight-CPU partition or an eight-CPU nonpartitioned system, the performance will be exactly the same. Partitions offer other advantages over other virtualization methods. Most notably, few changes to data center processes are required: Operating systems are installed and maintained in the same fashion as on non-virtualized systems.


7 Industry Examples Several products offer excellent hardware isolation. This section provides a representative list of examples. The rst server to use SPARC processors and Solaris to implement hard partitioning was the Cray CS6400, in 1993.

Sun Microsystems included Dynamic Domains on the Enterprise 10000 in 1997 and also in the Sun Fire family the midrange 4800, 4900, 6800, and 6900, and the large-scale F12K, F15K, E20K, and E25K systems. Dynamic Domains are also available in the follow-on M4000, M5000, M8000, and M9000 systems. Their implementation in the most recent generation is described in 2, Hard Partitioning: Dynamic Domains.

On the CS6400, E10000, and the following generation (4800-25K) of systems, this implementation provides complete electrical isolation between Dynamic Domains. There is no single point of failure in a domain that would affect all of the domains. However, a hardware failure of a component in the shared backplane can affect multiple domains.

Starting in 1993, Dynamic Domains could be recon gured without rebooting them. Hewlett-Packard s (HP s) nPars feature was rst made available on some members of the PA-RISC based HP 9000 series. It is also a feature of some of HP s Integrity systems.

In 2007, HP added the ability to recon gure these partitions without rebooting them. Amdahl s Multiple Domain Facility (MDF) and subsequently IBM s mainframe Logical Partitions (LPARs) are among the earliest implementations of hardwarebased partitioning, available since the 1980s. MDF and LPARs use specialized hardware and rmware to create separate execution contexts with assigned CPUs, RAM, and I/O channels.

A domain or partition may have dedicated physical CPUs or logical CPUs that are implemented on a physical CPU shared with other domains and shared according to a priority weighting factor. Physical RAM is assigned to one partition at a time, and can be added or removed from a partition without rebooting it..

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