HP Integrity Superdome SX2000 HP-UX 11i v3 Dynamic nPartitions - Features and - Page 7

Only floating cells are available for this type of replacement. You must reboot the partition to replace a base cell. Also, this is not the same as the "online replacement" available for PCI cards, which involves a temporary suspension of access and replacement with identical hardware configured into the identical state. Configuration recommendations for Dynamic nPartitions This section contains guidelines for optimizing the benefits of Dynamic nPartitions. Minimum amount of memory on base cells The operating system never places certain vital data elements in memory on floating cells. This is an important optimization to keep the operating system running at the highest possible performance level. Therefore, the system administrator must configure each partition with a sufficient number of base cells, or, more specifically, a sufficient amount of memory on base cells to meet the operating system requirements. The following table describes the rule for the total amount of physical memory present in the partition as compared to the minimum amount of memory on base cells. Physical memory (total in the partition) Minimum amount of memory on base cells 1 GB to 8 GB 1/2 of the physical memory 8 GB to 16 GB 4 GB 16 GB or more 1/4 of the physical memory If, as is typical, the same amount of memory is on each cell, with that amount being 8 GB or more, the rule can be stated simply: configure at least one-quarter of the cells in a partition as base cells. The ratio of the amount of memory on base cells to the amount of memory on floating cells can have significant performance implications. A partition with insufficient memory to place vital kernel data might not perform well. An important special case is the size of the HP Online JFS buffer cache. If the "autotune" option for the size of the HP Online JFS buffer cache is selected, the cache will be automatically resized upon Dynamic nPartitions operations. The consequence is that the buffer cache may be smaller on a system with many floating cells than on a comparable system comprised only of base cells. The smaller buffer cache may reduce the performance of certain file system operations, such as "find". The fact that floating cells must contain 100% cell local memory also influences the choice to configure a cell as base or floating. For workloads with strong and predictable memory locality, the use of cell local memory and process-to-processor affinity can yield significant performance improvements. Workloads that exhibit no memory locality may perform better with more interleaved memory. 7