Minmiss Hash; Weighted Real Servers - Avaya P330 User Manual

Chapter 1

MinMiss Hash

MinMiss hash distributes sessions to RSs in the same way as the Hash
metric. However, MinMiss hash retains persistency even when an RS is
removed from the group. When an RS fails or is removed, the load
balancer does not change the position of all the RSs in the list. Instead, it
redistributes the remaining RSs to the list entries freed by the failing RS.
The following figure illustrates how persistency is retained when an RS
becomes non-operational.
In the above figure, when Server 2 becomes non-operational, the list of
available servers is not readjusted. Only the list entries that are now
empty are replaced with other available servers. Therefore, persistency is
retained for all available servers. However, if Server 2 becomes
operational again, the list of available servers is recalculated so that the
smallest number of servers is affected. The list is not restored to its
original configuration. As a result, persistency is only partially recovered.

Weighted Real Servers

You can assign weights to RSs to enable faster RSs to receive a larger
share of sessions. This minimizes overloading and maximizes
functionality.
If you assign a weight to an RS, the sessions are distributed to the RSs in
the metric chosen (Round Robin, Hash or MinMiss). However, the
weighted RS is assigned a larger share of sessions. For example, if you
assign a weight of 20 to one RS and leave the default weight (10)on the
second RS, the weighted RS receives 2 sessions for each session directed
to the second RS. This is useful for RSs with different bandwidths or
processor speeds.
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Figure 1-9. MinMiss Metric - Persistency Retained
Avaya P330 Load Balancing Manager User Guide