“ fat tree ,a topology, which the data center hierarchy constructed on”
As you see from the above picture .
A data center has 3 layers.
1.Core layer
2.Aggregation layer
3.Edge layer
We can construct these layer with a help of a Topology which in graphs called a ‘fat tree’.
let K=4 ,
i e :- each switch has 4 ports.
Refer the above picture for the calculation done in the following steps.
STEP 1
K is called ‘pods’. Pods=K=4.
apply in formula , (k/2)²=core switches.
(4/2)²= 4 core switches.
STEP 2
Calculate switches for ‘pods’
Aggregation switches follows K/2=4/2=2 Aggregation layer switches.
Edge Switches follows K/2=4/2=2 Edge layer switches.
STEP 3
Edge Switches connected to their HOST/SERVER with a formula of K/2=No.of hosts/servers
In our case: POD refers the aggregation layer switches and E refers the Edge layer switches.
POD1 E1=4/2=2
POD1 E2=4/2=2
POD2 E1=4/2=2
POD2 E2=4/2=2
POD3 E1=4/2=2
POD3 E2=4/2=2
POD4 E1=4/2=2
POD4 E2=4/2=2
Sum all the POD1 E1 to POD4 E2. Now you get 16 HOSTS/SERVERS.
You can also derive the No.of HOSTS/SERVERS by simply substituting the formula K³/4 = 16.
You can set any value for K as per your requirement of HOSTS/SERVERS in End point.
