Virtual Partitions Overview


HP Virtual Partitions (vPars) allows the hardware of a single server to be divided into separate entities, each of which is capable of running a distinct operating system. This allows the workloads on multiple servers, none of which are fully utilizing their allocated hardware, to be combined to a single server and yet retain their operating system isolation. Figure 5-1 is a diagram showing three traditional servers running separate operating systems and workloads. Certainly the three workloads could be combined on one server without vPars; however, it is common for workloads to require some level of isolation. Operating system isolation is commonly used to provide the workload separation.

Figure 5-1. Workloads in a Non-Virtual Partition Environment


Figure 5-2 provides a view of a server running vPars. One of the key differences in this diagram is the Virtual Partition Monitor layer. This layer serves as an intermediary between the operating systems and the firmware. The vPar monitor reads the configuration of the Virtual Partitions from disk, loads the configuration into memory, and allocates resources to the Virtual Partitions based on the configuration. Using the vPar configuration information, the firmware calls of each of the operating systems are intercepted and filtered by the vPar monitor. For example, an operating system's firmware calls requesting data for the CPUs and I/O devices in the hardware platform will be filtered to return only the information for the assigned hardware resources. Consequently, applications built to run in non-vPar environments typically operate without modification because the interfaces between the HP-UX operating system and the workloads have remained unchanged.

Figure 5-2. Workloads in a Virtual Partition Environment


Virtual Partitions allow consolidation to a single server in order to increase system utilization. In addition, vPars allow dynamic CPU migration. The granularity and flexibility of vPars allow each workload to continue operating in a highly customizable environment. Each vPar is running a separate operating system, which means it can be patched and tuned precisely to the needs of the workload. Additionally, the operating system isolation results in protected workloads. An errant workload consuming all of the file descriptors, for example, will not affect any of the other vPars in the server. In addition, kernel panics and other software faults will not affect the availability of any vPar other than the one where the fault occurred.

Each vPar must consist of at least the following resources:

  • one bound CPU

  • sufficient memory to boot HP-UX and run a workload

  • I/O connectivity to bootable media

  • network connectivity (not required, but common)

Given these minimum system requirements, a large SD64000 Superdome with 64 processors is capable of running a maximum of 64 distinct virtual partitions. However, these virtual partitions cannot reside within a single nPartition. There can be at most eight vPars within each nPartition. To achieve the full 64 virtual partitions, the Superdome would first need to be divided into eight nPartitions, and each of the nPartitions can then be divided into eight virtual partitions. The final requirement for a Virtual Partition configuration is all the Virtual Partition kernels together must fit within the( lower 2GB of address space and each kernel must reside in contiguous address space.



The HP Virtual Server Environment. Making the Adaptive Enterprise Vision a Reality in Your Datacenter
The HP Virtual Server Environment: Making the Adaptive Enterprise Vision a Reality in Your Datacenter
ISBN: 0131855220
EAN: 2147483647
Year: 2003
Pages: 197

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