Technical data

ServerIron ADX Advanced Server Load Balancing Guide 59
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Other transparent cache switching options
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Setting the cache server weight
You can assign a performance weight to each server. Servers assigned a higher weight receive a
larger percentage of connections.
To set the weight for cache server1 to 5 from the default value of 1, enter the following commands.
ServerIronADX(config)# server cache-name server1
ServerIronADX(config-rs-server1)# weight 5
Syntax: weight <server-weight>
The <server-weight> variable may have any value from 1 though 65000. The default value is 1.
Enabling FastCache
By default, the ServerIron ADX uses cache responses to client requests as a means to assess the
health of the cache server. However, in an asymmetric topology where the cache server uses a path
to the client that does not pass through the ServerIron ADX, the ServerIron ADX does not observe
the return traffic. As a result, the ServerIron ADX concludes that the cache server has failed even
though the server may still be healthy.
When the ServerIron ADX concludes that a cache server is unavailable, the ServerIron ADX stops
sending client requests to the cache server. You can override this behavior by enabling the
FastCache feature. The FastCache feature configures the ServerIron ADX to continue sending client
requests to a cache server even if the ServerIron ADX does not see responses from the server.
To enable FastCache, enter commands such as the following.
ServerIronADX(config)# server cache-name server1
ServerIronADX(config-rs-server1)# asymmetric
Syntax: asymmetric
Enabling Remote Cache
When Proxy ARP is enabled on the router, the router informs the ServerIron ADX that it can respond
on behalf of the cache server. The ServerIron ADX uses ARP requests as part of the keep-alive
health-checking mechanism, so Proxy ARP enables the keep-alive health-checking mechanism to
function.
If Proxy ARP is disabled on the router, the keep-alive health-checking mechanism believes the
cache server cannot be reached, and does not mark the server ACTIVE or direct requests to the
cache server.
You can enable the ServerIron ADX to overcome the limitation posed by the absence of Proxy ARP
by enabling the remote cache feature for the cache server. To do this, enter commands such as the
following.
ServerIronADX(config)# server cache-name C1
ServerIronADX(config-rs-C1)# remote-cache
Syntax: [no] remote-cache
This example enables remote cache on cache server C1. With remote cache enabled, the
ServerIron ADX can perform health checks on the cache server, even though Proxy ARP is disabled
on the router connecting the ServerIron ADX to the cache server.