Even a fast disk will slow your application if there is too much disk I/O. If disk time and disk queue length are increasing from excessive read/write activity, the disk access may be a performance problem.
When examining disk access as it relates to performance, the disk I/O subsystem has many complex factors to consider. You should take into account the type and number of disk controllers, the type of disk drives, and the options required for fault tolerant configurations. Overall system performance can be dramatically affected by these configuration choices.
To improve disk access performance, it's important to use all available SCSI channels and to add more channels (if necessary). The addition of more disk drives will always help performance, especially if the disk I/O is random in nature. All drives have mechanical limitations that limit their performance while jumping from track to track and sector to sector. By adding more drives, the disk access can be handled more efficiently because some physical disk I/O can occur in parallel.
You can monitor disk I/O performance with the Windows NT Performance Monitor. If it indicates excessive disk I/O requests (or is trending higher), you should evaluate your application to determine when and why the disk access occurs. Sometimes, the overall data access strategy can be modified to significantly reduce disk usage.
If your disk is a performance bottleneck, you can:
Note You can easily monitor disk I/O use by using the Window NT Performance Monitor. For more information, see Using Performance Monitor in this chapter.