Technical data

Brocade ServerIron ADX Advanced Server Load Balancing Guide 99
53-1003441-01
Traffic distribution based on cache server capacity
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The seconds variable specifies the poll interval for the SNMP queries sent by the ServerIron ADX to
the cache servers. The ServerIron ADX then sets the cache state based on the reply received from
the cache server.
The following configuration sets Server Cache Group 1 to use the SNMP predictor configured with
the OID index 1 with the cs100 cache server.
ServerIronADX(config)#server cache-group 1
ServerIronADX(config-tc-1)#hash-mask 255.255.255.255 0.0.0.0
ServerIronADX(config-tc-1)#cache-name cs100
ServerIronADX(config-tc-1)#predictor snmp-weighted oid 1
Syntax: [no] predictor snmp-weighted oid oid-index
The oid-index variable specifies the index number for the SNMP object identifier that you want to
use for operating SNMP weighted load sharing for this cache group. This must be the same object
identifier as that defined under the cache servers.
A typical flow for SNMP-based cache server load balancing would include the following steps.
1. ServerIron ADX sends periodic SNMP queries to the cache server.
2. ServerIron ADX sets the cache server state based on the reply it receives from the cache
server.
3. For an incoming connection, a hash is computed based on its load state.
* In order to delete the existing connection on an offline/initializing cache server immediately the
server force-delete command needs to be configured.
** Overflow connections indicates that the connection that previously hashed to a cache server
that is currently either burdened, stressed, overloaded, overtaxed, halting or offline.
TABLE 10 Hash allocation and load balancing performed by ServerIron ADX doing Layer-4 TCS based on the
load state of the cache server
Cache server
state
Allocated hash
bucket
New connections Overflow
connections**
Existing
connections
Clears hash
buckets
Underused Yes Allows Allows Allows No
Normal Yes Allows Allows Allows No
Burdened Yes Allows Allows Allows No
Stressed Yes Allows (If no other
cache is
available)
Does not allow Allows No
Overloaded/
overtaxed
Yes Does not allow Does not allow Allows No
Halting No Does not allow Does not allow Allows Yes
Offline No Does not allow Does not allow Deletes* Yes
Initializing Yes Does not allow Does not allow Deletes* No