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.