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Configuration Guide

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» Configuration Requirements for nPartitions
» Configuration Recommendations for nPartitions
» CLM Configuration Recommendations
» Additional Information

Configuration Requirements for nPartitions

The hardware requirements shown below determine which cells are eligible to be assigned to an nPartition. To improve performance, you should also review the Configuration Recommendations for nPartitions and CLM Configuration Recommendations sections below.

  • All cells in an nPartition must have the same cell board type.

  • All cells in an nPartition must have the same processor revision level and clock speed. On PA-RISC systems, the IODC hardware version number (IODC_HVERSION) must be identical for all processors.

  • All cells in an nPartition must have the same firmware revision.

  • Each nPartition must have core I/O and a cell connected to an I/O chassis.

    • On servers based on the HP sx2000 chipset, core I/O is provided on each cell. On these servers, the active core cell can be different from the cell connected to an I/O chassis.

    • On all other nPartition servers, at least one cell in every nPartition must be connected to an I/O chassis that contains core I/O. Only one core I/O is active per nPartition. If an nPartition has multiple cells that are connected to I/O chassis with core I/O, only the core I/O connected to the active core cell is active.

Configuration Recommendations for nPartitions

For better performance and availability, you should configure nPartitions according to the following recommendations.

  • The DIMM configuration of each cell should include a multiple of two echelons per cell. This provides a performance improvement by doubling the cell's memory bandwidth (compared to having only one echelon installed). This is required for high availability; if one echelon fails, the cell still has at least one functional echelon of memory.

    Echelon 0 must be functional for a cell to boot.

  • If possible, install memory in multiples of 8 DIMMs.

  • A viable core cell should be connected to an I/O chassis that connects to a boot disk or other method of installing or recovering the operating system (such as a CD-ROM or DVD-ROM drive, network connection to an install server, or tape drive). This allows the nPartition to boot or recover the OS, even if only the nPartition's core cell is functioning.

    On servers based on the HP sx2000 chipset, core I/O is provided on each cell, so every cell is a viable core cell. On all other nPartition servers, a cell is a viable core cell only if it is attached to an I/O chassis with core I/O.

  • If possible, you should assign two or more core-capable cells to each nPartition. This allows the nPartition to boot at least to the system firmware user interface if a core cell fails to boot. On PA-RISC systems, BCH provides the boot device selection interface. The EFI Boot Manager provides the boot device selection interface on Itanium®-based systems.

    Some server configurations do not provide enough core-capable cells to satisfy this recommendation.

CLM Configuration Recommendations

The choice between interleaved memory and cell local memory (CLM) is dependent on the nature of the applications to be used in the nPartition. Cell local memory provides the best possible performance when it is accessed by processes running on the same cell that contains the memory. Interleaved memory provides the best possible performance when memory on one cell is accessed by CPUs on another cell.

Cell local memory is only supported on nPartitions running HP-UX 11i v2 (B.11.23), SuSE Linux Enterprise Server 9, or Microsoft® Windows®. If an nPartition is booted under an operating system that does not support CLM, any memory allocated as CLM will be unusable.

There are many factors that can determine an optimal mix of interleaved and cell local memory.

  • It is best to configure 100% cell local memory for nPartitions that boot Microsoft® Windows®.

  • The Complex Profile defines a minimum amount of interleaved memory that must be provided in each nPartition (0.5 GB). When the nPartition is booted, system firmware will enforce this minimum by adjusting the memory configuration if necessary.

  • The number of base cells that contribute to interleaved memory in an nPartition should be a power of 2. The amount of memory (in gigabytes) that is contributed to the interleave by each cell should also be a power of 2. This provides the best memory interleave and performance characteristics.

  • Each cell that participates in interleaved memory should contribute the same amount of memory to the interleave.

  • Some applications may be specifically designed to take advantage of CLM. Consult your application documentation for information about CLM and optimal memory allocation strategies.

  • In the absence of any specific knowledge about whether to use interleaved or cell local memory, it is best to use interleaved memory. This provides more predictable performance for any mix of applications. While cell local memory can give superior performance in the right circumstances, it can actually degrade performance when used inappropriately.

Additional Information

For additional information about configuration requirements and recommendations, refer to the following documents.

» HP Technical Documentation Server
» HP System Partitions Guide: Administration for nPartitions
» ccNUMA Overview

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