Windows 2000 Performance Guide

System Monitor Counters

A number of objects provide performance metrics that are relevant for evaluating and monitoring the performance of the disk I/O subsystem. The Physical Disk object provides information about each physical disk attached to the system. The Logical Disk object provides information about each partition. When a physical disk has been partitioned into multiple logical disks, the metrics provided by the Physical Disk object are aggregates of the load imposed on all the partitions. There are instances for each available partition and an instance that summarizes the counters over all partitions. A number of counters appear under both the Physical and the Logical Disk object. Note in particular that the _Total instance from the Logical Disk object aggregates the counters over all logical disks, and the Physical Disk object counters measure the load on a particular physical disk. When all the partitions are on the same disk, then the counters common to both objects will have the same value. But when there are multiple disks, the two sets of counters will not be equal. Note that the System object provides a few additional counters related to disk subsystem performance. Finally, the Cache and Memory objects provide some counters that are very useful in determining whether the cause of a disk bottleneck is filesystem access or a shortage of memory. In this chapter, we discuss the most important counters under the Physical Disk object, since we are focusing on the hardware ...