Virtual Machines vs Docker Containers

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Personal Website: https://nickjanetakis.com
Twitter: https://twitter.com/nickjanetakis
GitHub: https://github.com/nickjj

Transcript:

00:03

the first thing that you need to know is

00:05

docker containers are not virtual

00:08

machines back in 2014 when I was first

00:11

introduced to the concept of docker

00:13

containers I related them to being some

00:16

sort of lightweight or trimmed down

00:18

virtual machine the comparison made

00:21

sense because Dockers initial marketing

00:23

heavily leaned on it as something that

00:25

uses less memory and starts much faster

00:27

than virtual machines they kept throwing

00:30

around phrases like unlike a VM that

00:32

starts in minutes docker containers

00:35

start in about 50 milliseconds and

00:37

everywhere I looked there were

00:39

comparisons to VMs so once again docker

00:43

containers are not VMs now let's go

00:46

ahead and compare them side-by-side both

00:48

again by investigating what it looks

00:50

like to run in multiple applications on

00:53

a server using virtual machines one

00:56

layer at a time it all begins with some

00:58

type of infrastructure this could be

01:01

your laptop a dedicated server running

01:03

in a data center or a virtual private

01:06

server that you're using in the cloud

01:08

such as digital ocean or in Amazon ec2

01:12

instance on top of that server runs an

01:15

operating system on your laptop

01:17

this will likely be Mac OS Windows or

01:20

some distribution of Linux when we're

01:23

talking about VMs this is commonly

01:25

labeled as the host operating system

01:28

then we have a thing called the

01:30

hypervisor you can think of virtual

01:33

machines as a self-contained computer

01:35

packed into a single file but something

01:38

needs to be able to run that file that's

01:41

where a hypervisor comes into play and

01:43

there's two types of hypervisors first

01:46

our type 1 hypervisor x' that can

01:48

interface directly with your

01:50

infrastructures hardware the other is a

01:53

type 2 hypervisor which runs as an

01:56

application on top of your host

01:58

operating system we don't need to go too

02:01

deep into this but an example of type 1

02:03

hypervisor x' would be hyper kit on Mac

02:06

OS hyper-v on Windows and KVM on Linux

02:10

two popular type 2 hypervisors are

02:13

virtualbox and vmware usually type 1

02:16

hypervisor x' are more efficient because

02:19

they can bypass the host OS and interact

02:22

directly with the hardware of your

02:24

server but don't be thrown off by that

02:26

statement type 2 hypervisors are still

02:29

very efficient ok so the next layer in

02:32

this delicious server onion are your

02:35

guest operating systems let's say you

02:37

wanted to run 3 applications on your

02:40

server in total isolation that would

02:43

require spinning up 3 guest operating

02:45

systems which are all controlled by your

02:48

hypervisor they could all be the same

02:50

guest OS or different it doesn't matter

02:53

but the problem here is that each guest

02:56

OS in itself might be seven hundred

02:58

Meg's each that means you're using 2.1

03:01

gigs of disk space just for your guest

03:03

operating systems it gets worse too

03:06

because each guest OS needs its own CPU

03:09

and memory resources - there's a lot of

03:12

waste happening here then on top of that

03:14

each guest OS needs its own copy of

03:17

various binaries and libraries to lay

03:20

the groundwork down for whatever your

03:22

application needs to run for example you

03:25

might need lid PQ dev installed so that

03:28

your web applications library for

03:30

connecting to Postgres can connect to

03:32

your Postgres database if you're using

03:35

something like ruby then you would need

03:36

to install your gems

03:37

likewise with Python or no GS you would

03:41

install your packages just about every

03:43

major programming language has their own

03:45

package manager and you get the idea

03:47

since each application is different it's

03:49

expected that each app would have its

03:52

own set of library requirements finally

03:55

we have our application this is the

03:57

source code for whatever awesome

03:59

application you've built if you want

04:01

each app to be isolated you would need

04:03

to run each one inside of its own guest

04:06

OS so that's the story of running

04:09

virtual machines on a server now let's

04:12

compare that to docker containers docker

04:14

containers aren't adjectives we still

04:17

need some type of infrastructure to run

04:19

them like VMs this could be your laptop

04:22

or a server somewhere out there in the

04:24

cloud then we have our host operating

04:27

this could be anything you want that's

04:29

capable of running docker all major

04:32

distributions of Linux are supported and

04:34

there are ways to run docker on Mac OS

04:36

and Windows - ah finally something new

04:40

the docker Damon replaces the hypervisor

04:42

the docker Damon is a service that runs

04:45

in the background on your host OS and

04:47

manages everything required to run and

04:50

interact with docker containers we'll go

04:53

into much more detail on the dr. Damon

04:55

later on in this section next up we have

04:58

our binaries and libraries just like we

05:01

do on virtual machines but instead of

05:03

them being ran on a guest OS they get

05:06

built into special packages called

05:07

docker images then the doctor daemon

05:10

runs those images the last piece of the

05:13

puzzle is our applications each one

05:15

would end up residing in its own docker

05:17

image and will be managed independently

05:20

by the doctor Damon

05:21

typically each application and its

05:24

library dependencies get packed into the

05:26

same docker image as you can see each

05:28

application is still isolated and just

05:31

in case you didn't notice there's a lot

05:33

less moving parts with docker we don't

05:35

need to run any type of hypervisor or

05:37

virtual machine

05:39

instead the doctor daemon communicates

05:41

directly with the host operating system

05:43

and knows how to ration out resources

05:45

for the running docker containers it's

05:48

also an expert and ensuring each

05:50

container is isolated from both the host

05:52

OS and other containers the real-world

05:55

difference here means instead of having

05:57

to wait a minute for a virtual machine

05:59

to boot up you can start a docker

06:01

container in a few milliseconds you also

06:03

save a ton of disk space and other

06:06

system resources due to not needing to

06:08

lug around a bulky guest OS for each

06:11

application that you run there's also no

06:14

virtualization needed with docker since

06:16

it runs directly on the host OS what

06:18

that said don't let this lecture jade

06:21

your opinion of virtual machines both

06:23

VMs and docker have different use cases

06:25

in my opinion the virtual machines are

06:28

very good at isolating system resources

06:31

and entire working environments for

06:34

example if you owned a web hosting

06:36

company you would likely use virtual

06:38

machines to separate each customer

06:40

on the flipside Dockers philosophy is to

06:43

isolate individual applications not

06:46

entire systems a great example of this

06:49

would be breaking up a bunch of web apps

06:51

into their own Gawker images and we'll

06:54

go into more detail on the topic of when

06:56

you should use a VM verse stacker in

06:58

another lecture and don't worry if you

07:00

didn't fully understand this lecture

07:02

it's a very deep topic with a lot of

07:04

moving parts and technologies so let me

07:07

solidify everything with a brilliant

07:09

analogy that a once read from one of

07:11

Dockers guides you can think of virtual

07:14

machines as houses and you can think of

07:17

docker containers as apartment houses

07:20

are fully self-contained

07:21

and offer protection from unwanted

07:24

guests they also each have their own

07:26

infrastructure plumbing heating

07:29

electrical systems and so on in addition

07:32

to that most houses are going to have at

07:35

least a bedroom living area bathroom and

07:38

a kitchen if you only want a place to

07:41

sleep in poop it's going to be very hard

07:43

to find a house that meets those

07:44

requirements you'll very likely end up

07:47

buying more than you need because that's

07:49

how houses are built Apartments on the

07:51

other hand also offer protection from

07:54

unwanted guests but they are built

07:56

around a shared infrastructure each

07:58

apartment building offers shared

08:00

plumbing heating electrical systems and

08:03

so on to each apartment also apartments

08:06

can be bought in various sizes you can

08:09

buy a very small studio all the way to a

08:12

penthouse suite you are free to pick a

08:15

size that matches your exact needs so to

08:18

wrap things up docker containers share

08:21

resources with your host OS through the

08:23

doctor Damon whereas virtual machines do

08:26

not hopefully that clears things up for

08:28

you but now you might have a few other

08:30

questions such as how do I tell when I

08:33

should use a virtual machine or docker

08:35

containers or maybe you're even

08:37

wondering if docker containers are

08:39

compatible with virtual machines both

08:42

are very reasonable questions to ask and

08:44

I'll answer both of them in the next

08:46

lecture see you there