Expiration

  If the News Cache is running for a longer time the cache's database grows and older articles must be eliminated to free disk space. The following strategies are available for the replacement of older articles.

Random

expires news articles in a random manner. This method is rather unintelligent and should be avoided.

Least Recently Used

expires the articles that have not been accessed for the longest period first.

Least Frequently Used

expires articles that have been least frequently used first, because those articles are least likely accessed again.

Oldest Article First

expires the oldest article first. These articles are unlikely to be accessed again, because they have already been read by most news readers and they will expire first on the news server.

Biggest Article First

expires those articles with the biggest size first. This eliminates articles usually found in binary groups. The elimination of these articles costs the least time and brings the most disk space benefit.

In the current version of the News Cache we decided to use the Oldest Article First strategy. Statistics for these expiration methods are required for a detailed discussion. This will be done in a future work (see section 8.1.3).