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nPartition Administrator's Guide > Chapter 3 Planning nPartitions

Recommended nPartition Configurations


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For best performance and availability, configure nPartitions to meet the following guidelines.

  • On servers based on the HP sx1000 chipset or HP sx2000 chipset, the nPartition memory configuration should meet the following guidelines:

    • The number of cells participating in memory interleave should be a power of two, and each cell participating in interleave should contribute the same amount of memory.

    • The total amount of memory being interleaved should be a power of two number of GBytes.

  • When configuring cell local memory, ensure that the amount of interleaved memory meets the guidelines given here. (All memory not specified as being cell local will be interleaved.)

    Also ensure that any nPartition that has cell local memory configured runs only operating systems that support cell local memory.

    Cell local memory can be configured on servers based on the HP sx1000 chipset or HP sx2000 chipset.

    CAUTION: Memory configured as cell local memory only can be used by operating systems that support it.

    Any memory configured as cell local memory is unusable when an nPartition runs an operating system that does not support it.

  • The I/O chassis containing the active core I/O also should have an operating system (OS) boot disk and method of installing or recovering the OS (such as a CD-ROM/DVD-ROM drive, network connection to an install server, or tape drive). This applies to first-generation cell-based servers and HP sx1000-based servers; it allows the nPartition to boot or recover the OS, even if only the core cell for the nPartition is functioning. On HP sx2000-based servers, every cell has core I/O.

  • Assign multiple core-capable cells to each nPartition.

    This allows the nPartition to boot at least to the system boot environment (either BCH or EFI) if a core-capable cell fails to boot. On HP sx2000-based servers, every cell has core I/O.

    (Disregard this recommendation if you are configuring multiple nPartitions in a cell-based server that has only two core-capable cells.)

  • The memory configuration of all cells in an nPartition should be identical to achieve best performance.

    Each cell in an nPartition should have:

    • the same number of DIMMs

    • the same capacity (size) and the same locations (population) of DIMMs

    This avoids cell interconnect (crossbar) "hot spots" by distributing memory evenly across all of the cells in the nPartition.

  • The memory configuration of each cell should include a multiple of two memory ranks (first-generation cell-based HP 9000 servers) or a multiple of two memory echelons (servers based on the HP sx1000 chipset or HP sx2000 chipset) per cell.

    On the first generation of cell-based HP 9000 servers, each memory rank is 4 DIMMs. If possible, install memory in sets of 8 DIMMs: 8 DIMMs or 16 DIMMs on HP rp7405/rp7410, rp8400, and Superdome (SD16000, SD32000, SD64000) cells. On Superdome cells, you also can install 24 DIMMs or 32 DIMMs per cell.

    On servers based on the HP sx1000 chipset or HP sx2000 chipset, each memory echelon is 2 DIMMs. If possible, install memory in sets of 4 DIMMs: 4, 8, 12, or 16 DIMMs. On Superdome servers, you also can install 20, 24, 28, or 32 DIMMs per cell.

    This provides a performance improvement by doubling the memory bandwidth of the cell, as compared to having one memory rank or memory echelon installed.

    This also can provide an availability improvement, in that if one memory rank or echelon fails the cell still has at least one functional rank of memory.

    (Memory rank 0, or echelon 0, must be functional for a cell to boot.)

  • Each nPartition should have PRI (primary), HAA (high-availability alternate), and ALT (alternate) boot paths defined and configured, and their path flags appropriately configured for your purposes.

    NOTE: Note that on HP Integrity servers, the PRI path corresponds to the first item in the EFI boot options list, the HAA path is the second item in the boot options list, and ALT is the third boot option.

    The PRI and HAA paths should be configured to reference disks that are connected to different cells, if possible, with HAA being a mirror of the root volume and PRI being the root volume. ALT should be the path of a recovery or install device.

    Under this configuration, if the cell to which the PRI disk is connected fails or is otherwise inactive and the cell to which the HAA disk is available, then the nPartition still can boot an operating system.

    Even if the PRI and HAA devices connect to the same cell (such as on a two-cell server with two nPartitions configured), the HAA device can be used to boot an operating system should the PRI device fail.

Recommended HP Superdome nPartition Configurations

On HP Superdome servers, the locations of the cells you assign to each nPartition and the resulting loads on server interconnections can affect nPartition system performance within the server.

HP offers specific guidelines for configuring nPartitions on HP Superdome servers in order to ensure good system performance.

NOTE: The guidelines in this section apply to HP Superdome servers only.

These guidelines follow two basic configuration principles:

  1. Avoid sharing interconnecting hardware (crossbars and crossbar links) among multiple nPartitions.

  2. Minimize the number of crossbar links used by each nPartition, but do not overload crossbar links by creating nPartitions that can generate more cell communications traffic across the links than the links can support. Overloading crossbar links degrades performance.

Configuration Guidelines for HP Superdome nPartitions. Use these guidelines to help determine which cells to assign to the nPartitions you create on HP Superdome servers.

  • Define nPartitions in order of size.

    Assign cells to the nPartition that has the largest cell count first. Then select cells for the next largest nPartition, and so on, and finally choose cells for the nPartition with the fewest cells last.

    This provides more appropriate cell assignments for larger nPartitions (those with more cells). Any smaller nPartitions with fewer cells are more easily accommodated in the remaining, available cells.

  • Place each nPartition within an empty cabinet, if possible.

    This applies to nPartitions in HP Superdome 64-way servers only.

    If possible, assign each nPartition cells from a cabinet whose cells have no nPartition assignments. Do this before assigning cells from a cabinet that already has cells assigned to an nPartition.

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