HP P4000 9.0 HP StorageWorks P4000 SAN Solution User Guide - Page 281
Performance monitoring and analysis concepts, Workloads, Access type, Access pattern, Queue depth
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Performance monitoring and analysis concepts The following general concepts are related to performance monitoring and analysis. Workloads A workload defines a specific characterization of disk activity. These characteristics are access type, access size, access pattern, and queue depth. Application and system workloads can be analyzed, then described using these characteristics. Given these workload characterizations, test tools like iometer can be used to simulate these workloads. Access type Disk accesses are either read or write operations. In the absence of disk or controller caching, reads and writes operate at the same speed. Access size The size of a read or write operation. As this size increases, throughput usually increases because a disk access consists of a seek and a data transfer. With more data to transfer, the relative cost of the seek decreases. Some applications allow tuning the size of read and write buffers, but there are practical limits to this. Access pattern Disk accesses can be sequential or random. In general, sequential accesses are faster than random accesses, because every random access usually requires a disk seek. Queue depth Queue depth is a measure of concurrency. If queue depth is one (q=1), it is called serial. In serial accesses, disk operations are issued one after another with only one outstanding request at any given time. In general, throughput increases with queue depth. Usually, only database applications allow the tuning of queue depth. Changing the sample interval and time zone You can set the sample interval to any value between 5 seconds and 60 minutes, in increments of either seconds or minutes. The time zone comes from the local computer where you are running the CMC. You can change the sample interval in the following ways: • Using the toolbar • In the Edit Monitoring Interval window, where you can also change the time zone To change the sample interval from the toolbar: 1. In the navigation window, log in to the management group. P4000 SAN Solution user guide 281
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