Using Cache Statistics

The PC-CacheFS Monitor displays statistics that allow you to monitor performance. Click on the View Statistics button to expand the monitor. The monitor displays the cache-hit rate, the capacity, and the relative performance.

Cache-Hit Rate

PC-CacheFS retrieves file or directory information from a network drive and moves the information into the cache, stored on your local hard drive. Also, PC-CacheFS makes consistency checks between the cache and the remote location, and updates the cache.

A hit occurs when the information in the source network drive is current with the information in the cache. A miss occurs when the information on the source network is more recent than the information in the cache.

The average of the number of hits to the total number of hits and misses is referred to as the cache-hit rate, and is displayed in the Cache-hit Rate graph.

Factors Affecting the Cache-hit Rate

The cache-hit rate is affected by the type of access, the size of the cache, and the frequency of the consistency checks.

Type of Access

The way you access your files affects the cache-hit rate. If you access many files and you have a large cache, you will have a larger cache-hit rate because older information still remains in the cache during consistency checks. However, if you have a small cache, there is less room for information to remain. As the cache fills, older information is automatically removed from the cache. You will experience more misses and a lower cache-hit rate.

Cache Size

The cache size implies cache capacity. The larger the cache, the better the chances are that least recently accessed information remains in the cache and has not been automatically removed. The smaller the cache, the more likely that least recently accessed information will be removed from the cache.

Frequency of Consistency Checks

The file and directory time-out values affect the frequency with which PC-CacheFS performs consistency checks. When information on the network drive changes, PC-CacheFS updates the cache. These instances are misses and result in a lower cache-hit rate.

Capacity

The In Use graph monitors the capacity of the cache. The In Use statistic fluctuates as you access new files from a network drive and the information is added to your cache. When your cache is full, capacity reaches 100% on the In Use graph. As the cache becomes updated with new information from the source network drive, the least recently accessed information is automatically removed from the cache to make space available for the new information.

Relative Performance

Your most precise indicator of cache effectiveness is the relative performance value displayed in the PC-CacheFS Monitor. After you restart your computer, relative performance displays at 100 percent, which indicates that the system performance is the same as without PC-CacheFS. As you retrieve information from a remote location, the relative performance increases or decreases to indicate the overall gain or loss of performance for your particular mix of applications. A low relative performance may indicate that while your network is fast, your local disk, where your cache is located, may be slow.

A relative performance under 100 percent can occur when PC-CacheFS automatically updates information in the cache, slowing the speed of your system below your regular system speed. A continued relative performance below 100% indicates you are not using the information on the current drive enough times to necessitate caching that particular network drive. Select a different drive to cache; one on which you use information more frequently.

Since PC-CacheFS has the benefit of reducing network traffic and server load, a slightly lower relative performance may indicate increased productivity across multiple clients at your site. A high relative performance indicates that your cache is performing well in relation to the network, thereby enhancing your personal productivity. Other indicators of cache effectiveness include an average cache-hit rate greater than 50 percent, and green lights in the Hits field more often than yellow lights in the Misses field.

Resetting Cache Statistics

Over time, PC-CacheFS accumulates statistics about your cache, such as the cache-hit rate and total kilobytes (KB) read. If you want the fields in the PC-CacheFS Monitor to display the statistics for a particular drive, you can reset the statistics. By resetting the statistics, you can determine the changes of statistics for a particular drive over time. You can also find out how one particular drive contributes to cache performance overall.

Reset cache statistics by expanding the PC-CacheFS Monitor and clicking Reset Statistics.