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Catching Up a Backlog

A backlog of the current newsfeed can occur if the news server has shut down (e.g. due to maintenance work) or lost the network connection for some time. This backlog is difficult to catch up during regular operation, because of the heavy I/O-load caused by the update process parallel to the news reading clients and the normal news operation.

**Abbildung 3.2:** Configuration with a server side News Cache
$\begin{figure} \begin{center} \leavevmode \epsfig {file=eps/serversidecache.eps} \end{center}\end{figure}$

The I/O-load on the news server can be reduced by reducing the number of accesses to the news database, which can be accomplished by the provision of a server side news cache. Clients will connect to the news cache instead of the news server as shown in Figure 3.2. The cache server can identify duplicate requests and issues these requests to the news server only once, thus reducing the number of requests made to the news server's news database.

gschwind@infosys.tuwien.ac.at