Two types of clusters are supported: soft clusters and management-only clusters. A soft cluster consists of multiple appliances that use an external clustering device such as an L4 Switch or router to handle load balancing and routing responsibilities. A management-only cluster also consists of multiple appliances whose functions are managed through a proprietary communications protocol accessible through the Manager UI. A management-only cluster does not use an external clustering device.

For more information about clustering, see Clustering‚ on page 144.

Transparency

The Intel NetStructure Cache Appliance can transparently intercept NNTP traffic bound for a well known NNTP server. By transparently intercepting, caching, and serving the NNTP data from a centralized parent news server, the appliance simplifies migration and administration while both increasing responsiveness and decreasing network use.

Posting

The Intel NetStructure Cache Appliance sends user article postings to the parent news server. You can specify the parent news server that receives postings for a particular group or set of groups from the command-line interface. For procedural information, see Configuring NNTP servers‚ on page 65. When acting as the news server (accepting article feeds), the appliance accepts postings.

With background posting, the appliance queues posted articles until the posting news server can accept the posted article.

Maintaining the cache: updates and feeds

The Intel NetStructure Cache Appliance can maintain the freshness of its cache by:

Updating its cache on demand

Actively retrieving (pulling) updates at configured intervals

Accepting news feeds

You can configure the following options from both the Manager UI and the command-line interface:

Pull the overview information for specified groups:

For all groups designated as pullover, the server will retrieve the overview database information (using the OVER/XOVER commands) automatically and periodically. Pulling overview information can be useful for high volume groups that are frequently read but from which only a subset of the articles are accessed.

Appendix A Caching Solutions and Performance

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Intel 1520 manual Transparency, Posting, Maintaining the cache updates and feeds