Data center adamish

What is the task of access switch in data center

access points of the host, where host connects to the network

A leaf switch has 4 ports to upwards direction, how many spine switches are in this array

4
In a leaf-spine network, each upward-facing port on a leaf switch typically connects to a different spine switch. So there the same amount of spine switches as leaf switches pointing upwards.

We use switches with 6 ports in fat tree topology, how many spine switches are in a Pod?

3
In a fat-tree network, the number of spine (aggregation) switches in one pod is: k/2. Where k is the number of ports on each switch.

Simple idea - A fat-tree splits the switch ports into two equal groups:

Half the ports connect downward

Half the ports connect upward

Because a 6-port switch splits into:

3 down

3 up

What is the main advantage and disadvantage of spine and leaf architecture

Advantage(egzo):
supports east-west traffic

Disadvantage:
Needs more cables and more switches

Name all HPC types (3)

Type 1(tightly coupled)
Type 2
Type 3 (loosely coupled)

What is the Type 3 (loosely coupled) High performance cluster used for?

dividing up and distributing file for manipulation in parallel (parallel manipulation)

Formula of oversubscription

Total output bandwidth / input bandwidth (down/up)

A switch is connected to its upper layer by 2×10Gbit/s, while to its lower layer by 20×2 Gbit/s. How much is the oversubscription?

40/2 = 2

What are the main advantages of the fat tree architecture? Name 2 of them

Simple devices

Great scalability

In a spine and leaf architecture, we use 64-port switches. A spine switch has 12 connections to the core layer. How many leaf switches can we have in maximum configuration?

52
We have 64 ports total, 12 of them are connected to the core layer, so the remainder can be connected to the leaf switches

You would provide a service based on virtual machines. What data center configuration would you choose

Spine and leaf architecture

Because Spine and leaf architecture specifies in east and west traffic and VM traffic is mostly server-to-server communication inside the data center.

Why other architectures don’t work:
Traditional architecture - would work but not ideal for VM
Fat tree - would work as well, but spine and leaf are simpler and more commonly used

You would provide a service based on mostly client-to-server traffic. What data center configuration would you choose

Traditional tree architecture, because its good with older enterprise networks with mostly client-to-server traffic.

You would provide a service based vert large HPC systems. What data center configuration would you choose

Fat-tree, because its designed for high bandwidth and parallel paths. More often discussed in networking theory or very large HPC systems.

A leaf has 6 ports to upward direction. How many spine switches are in this array?

6
In a spine-and-leaf architecture each leaf switch connects upward to the spine switches

If the leaf has 6 upward ports, then it can connect to:

6 uplinks=6 spine switches6 \text{ uplinks} = 6 \text{ spine switches}6 uplinks=6 spine switches

We use switches with 16 ports in a fat tree topology. How many aggregation switches are in the Pod?

In a fat-tree topology, the number of aggregation switches in one pod is: k/2
Since the switches have 16 ports: k/2=16/2=8
Answer: 8

We create a two-level data center structure from Top of Rack (ToR) switches. What is the biggest disadvantage of the solution?

Disadvantage: Limited scalability
Because in a two-level design(design where ToR is used):

Servers connect to ToR switches

ToR switches connect directly to higher-level switches

And when data center grows - the number of required connections increases quickly