Cloud computing theory and practice

Question 1

5 characteristic of cloud computing

Answer 1

On demand self service access
Broad network access
resource pooling
rapid elasticity
measured service

Question 2

Entities involved in cloud computing

Answer 2

customer
provider
carrier (ISP)
broker (manage use performance and delivery of cloud services)
auditor (performs security audit)

Question 3

DBaaS

Answer 3

Database as a service, db are stored in the cloud provider infrastructure, provides scalability self service

Question 4

IaC

Answer 4

Infrastructure as code, a way to automate cloud infrastructure through code, most used tools are ansible and terraform

Question 5

S3

Answer 5

Simple storage system, service from AWS, stores data in objects inside buckets

Question 6

EBS

Answer 6

Elastic Block store, provide storage volumes to EC2 instances, an instance can have more volumes but not the opposite

Question 7

Lambda

Answer 7

AWS service that provide serverless execution of code on demand

Question 8

Availability zones

Answer 8

Datacenter with 50 000 to 80 000 servers, each region has at least 2 AZ

Question 9

WSC (Warehouse scale computer)

Answer 9

Computers in cloud provider’s datacentes composed by cells and racks, WSC can be managed through Borg (Cluster management system)

Question 10

Borg

Answer 10

Is a cluster management system for WSC, it include a Borgmaster (controller) and Borglets (controlled machines)

Question 11

Kubernetes

Answer 11

it’s a cluster manager for containers, includes a master server that manage workload on minions or workers

Question 12

Kubernetes scheduler

Answer 12

It allows management of workers resources by the master server

Question 13

Kubernetes Pods

Answer 13

Are groups of container used as a unit of scheduling, deployment and replication, pods allow multiple containers to run an application

Question 14

2 types of VM

Answer 14

Process VM - executed for a specific process once terminated the VM will be stopped
System VM - VM with an OS and many processes

Question 15

Hybrid hypervisor

Answer 15

hypervisor that shares the hardware with another os

Question 16

QEMU

Answer 16

QEMU can virtualize or emulate any components on a physical machine

Question 17

Virtualization vs emulation

Answer 17

1) virtualization is based on an hypervisor that abstract the hardware so that it can be shared between multiple VMs, the VMs run on a portion of the hardware
2) Emulation is the process with which you alterate the hardware via a software to make a program that didn’t support the hardware run on it

Question 18

QEMU 4 modes

Answer 18

• usermdoe emulation for code compilation and debugging
• system emulation supports VMs on a physical emulated system
• KVM hosting supports deployment and migration of KVM images
• Xen hosting emulates the hardware and allows execution of VMs with Xen

Question 19

KVM

Answer 19

Kernel based virtual machine, is an hypervisor buildt with linux kernel

Question 20

KVM components

Answer 20

KVM-loadable module provides management of the hardware
KVM platform emulation provided by a version of QEMU

Question 21

KVM advantages

Answer 21

Open source
Performance
Cross-platform
Simplicity

Question 22

Paravirtualization

Answer 22

The guest OS knows it’s running on a virtualized environment that allows VMs to communicate with the hypervisor via API, that results in better performance

Question 23

Xen

Answer 23

Hypervisor that use QEMU as device emulator and supports paravirtualization

Question 24

Nested virtualization

Answer 24

situation where an hypervisor is a guest OS of another hypervisor

Question 25

SAN

Answer 25

Storage Area network, interconnect server with storage that uses fiber channel

Question 26

Fiber channel

Answer 26

Protocol based on 7 layers:
- Physical layer
- Transmission protocol (encode/deocde data)
- Signaling protocol (framing and flow control)
- Common services layer
- Protocol mapping layer
Fiber channel uses ID instead of a mac address

Question 27

CDN (Content delivery network)

Answer 27

Offer better performance with replication and caching of data on servers, 2 types of servers:
- Origin servers -> data updated by the content provider
- Replica servers -> cache data and serve as data source for clients

Question 28

Storage models

Answer 28

models that describe the layout of a data structure in a physical storage, 2 commonly used models:
- Journal
- Cell storage

Question 29

Journal vs cell storage models

Answer 29

Cell storage divide the storage in same size cells and objects to store are the same size of cells
Journal storage consists of a manager and a cell storage where the entire history of a variable is stored instead of just the current value

Question 30

DBMS (Database management system)

Answer 30

system that can manage the database, it supports a query language that is a dedicated programming language for interacting with databases

Question 31

NoSQL

Answer 31

Is a DBMS that doesn’t rely only on SQL, is mostly useful with big quantity of data that don’t need a relational model

Question 32

NoSQL databases type

Answer 32

Document store -> memorize documents in JSON, XML or BSON formats
Key-Value
Colummn-family -> stores tables with many rows and few columns
Graph -> graph datastructures used to represent and memorize data

Question 33

Distributed File System (DFS)

Answer 33

It’s a way to group data logically in the same place even if distributed across the network. An example of DFS is NFS.

Question 34

NFS (Network file system)

Answer 34

DFS based on UNIX, has 3 major characteristic:
- Layered design flexibility
- Hierarchical design for scalability (files in direcotries)
- Systematic design with metadata (file owners, access rights)

Question 35

Stateless servers

Answer 35

Servers that don’t require a connection to be made but respond directly do clients, client requests are seen as independent transactions