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Complementary Performance Technologies

IBM System z* High Performance FICON* (zHPF) technology was created to allow more efficient execution of frequent I/O requests. It allows operations to remain queued in storage subsystems rather than retransmitted after busy conditions. Better workload management results from storage subsystems management of I/O operation execution order after device reserves are released. The zHPF technology can also quadruple I/O rate capabilities without additional channel, control-unit or switch ports.

In the zEnterprise* EC12 servers, IBM has enhanced the channel path selection algorithm used to choose routes for executing storage I/O requests. It steers traffic away from congested channel paths and control-unit ports toward channel paths experiencing better initial command response times. Multisystem congestion is managed using the comprehensive I/O measurements.

The IBM DS8000* mainframe storage supports many autonomic I/O enhancements. The adaptive multistream prefetch (AMP) algorithm improves cache management efficiency, reducing time required to satisfy cache misses. The DS8000 algorithm uses hints provided by middleware running under z/OS*, and itself decides how much data to pre-fetch asynchronously from disk. AMP adjusts pre-fetching based on the applications’ need to avoid overutilizing disks when the applications don’t require the resources. DS8000 also implements Wise Ordering of Write to minimize head movement at backend drives.

With Easy Tier* technology, the DS8000 subsystems learn data usage patterns over time to proactively promote “hot” data to faster devices such as SSD to help optimize application performance, and demote “cold” data to slower devices.

—H.M.Y.

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