The server farm consists of a logical grouping of cache servers. Each server farm belongs to a web cache. TWCB supports the configuration of up to five server farms that can be associated with the web cache.
There are three aspects to configuring a server farm:
You create a server farm by naming it. Upon naming a server farm, you are placed in web cache server farm configuration mode. The cache server is the IP address of the actual transparent proxy web cache server.
The default behavior for selecting a cache from a server farm is to use a hash of the destination IP addresses. Should a single cache server be associated with one or more heavy traffic destination IP addresses, then the round robin selection mechanism can be used to balance traffic to particular ranges of destination IP addresses among the caches configured to the server farm.
In Predictor Round-Robin Overview we see how requests destined for one particular destination IP, configured for standard caching, only accesses cached web objects from the cache server where its cache resides. In this case, the destination IP addresses reside on the s1IPv6Server server farm 4000:1:2::6 cache server. The s2IPv4Server server farm is configured with a predictor round-robin list. Each list member has its web objects cached across all the cache servers on the s2IPv4Server server farm.
The predictor round-robin feature allows for the creation of up to 10 user lists. Members of a predictor round-robin list no longer have a single cache on a single cache server. Instead, web objects for list members are cached across all cache servers associated with this server farm in a round robin fashion. A server farm with a configured predictor of round-robin will only cache members of predictor round-robin lists associated with that server farm.
In an IPv6 TWCB server farm round robin context, you must use an IPv6 access list to define the cache servers used by the round robin. In an IPv4 TWCB server farm round robin context, you can either use an IPv4 access list or specify a beginning and end IP address for a range of cache servers.
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