Performance Monitoring And Analysis Concepts; Workloads; Access Type; Access Size - HP StorageWorks P4000 User Manual

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.
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