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[ 1. EC2 Instance Launch Types ]

1. On Demand Instances : short workload, predictable pricing

2. Reserved: (Minimum 1year)

  - Reserved Instances: long workloads

  - Convertible Reserved Instances: long workloads with flexible instances

  - Scheduled Reserved Instances: eg. every Thursday between 3 and 6 pm

3. Spot Instances: short workloads, for cheap, can lose instances (less reliable)

4. Dedicated Instances : no other customers will share your hardware

5. Dedicated Hosts: book an entire physical server, control instance placement

1. EC2 On Demand

필요시에만 사용, 비쌈

- Pay for what you use (billing per second, after the first minute)

- Has the highest cost but no upfront payment

- No long term commitment

- Recommended for short-term and un-interrupted workloads, where you can't predict how the application will behave.

2. EC2 Reserved Instances

선불제, 비교적 저렴

- Up to 75% discount compared to On-demand

- Pay upfront for what you use with long term commitment

- Reservation period can be 1 or 3 years

- Reserve a specific instance type

- Recommended for steady state useage applications(think database)

* Convertible Reserved Instance

  - can change the EC2 instance type

  - Up to 54% discount

* Scheduled Reserved Instances

  - launch within time window you reserve

  - When you require a fraction of day/week/month

3. EC2 Spot Instances

여유자원을 싸게 사용하는 방식으로 사용자가 최대 입찰 가격을 정해놓고 사용, 가격이 최대가격이상이 되면 중지

- Can get a discount of up to 90% compared to On-demand

- Instances that you can "lose" at any point of time if your max prices is less then the current spot price

- The Most cost-efficient instances in AWS

- Useful for workloads that are resilient(회복력있는/탄력적인) to failure

  eg. Batch jobs, Data analysis, Image processing

- Not great for critical jobs or databases

- Great combo : Reserved Instances for baseline + On-Demand & Spot for peeks

- Define max spot price and get the instance while current spot price < max

- The hourly spot price varies based on offer and capacity

- If the current spot price > your max price, you can choose to stop or terminate your instance with a 2 minutes grace period

[ # Other strategy : Spot Block ]

  "block" spot instance during a specified time frame (1 to 6 hours) without interruptions

  * In rare situations, the instance may be reclaimed

[ # How to terminate Spot Instances ]

Spot request 설정시 지정한 request type 에 따라, 설정한 max price 에 도달했을 때의 인스턴스 동작이 달라짐

 1) one-time : 설정한 spot request 가 인스턴스 런칭과 함께 사라짐. max price 도달시 인스턴스 stop or terminate.

 2) persistent : 설정한 spot request 가 남아, 인스턴스가 terminated 돼도 인스턴스를 다시 런칭시킴

* persistent request type 인 경우, spot request 를 먼저 cancel 한 후, spot instance를 terminate 시켜야 함

* You can only cancel Spot Instance requests that are open, active, or disabled.

  (open/active/disabled 상태일 때만 spot request 제거 가능)

4. EC2 Dedicated Hosts

사용자 전용의 물리적 서버, 딮한 설정 가능

- Physical dedicated EC2 server for your use

- Full control of EC2 Instance placement

- Visibility into the underlying sockets/physical cores of the hardware

- Allocated for your account for a 3 year period reservation

- More expensive

- Useful for software that have complicated licensing model

  Or for companies that have strong regulatory or compliance needs

5. EC2 Dedicated Instances

계정에 귀속된 인스턴스

- Instances running on hardware that's dedicated to you

- May share hardware with other instances in same account

- No control over instance placement (can move hardware after Stop/Start)

[ Spot Fleets ]

- Spot Fleets = set of Spot Instances + (Optional) On-Demand Instances

- The Spot Fleet will try to meet the target capacity with price constraints

  1) Define possible launch pools: instance type (m5.large), OS, AZ

  2) Can have multiple launch pools, so that the fleet can choose

  3) Spot Fleet stops launching instances when reaching capacity or max cost

- Strategies to allocate Spot Instances:

  1) lowestPrice : from the pool with the lowest price (cost optimization, short workload)

  2) diversified : distributed across all pools (great for availability, long workloads)

  3) capacityOptimized : pool with the optimal capacity for the number of instances

* Spot Fleets allow us to automatically request Spot Instances with the lowest price

[ 2. EC2 Instance Types ]

R : appliations that needs a lot of RAM - in-memory caches

C : applications that needs goods CPU - compute/databases

M : applications that are balanced (think "medium") - general/web app

I : applications that need good local I/O (instance storage) - databases

G : applications that need a GPU - video rendering/machine learning

T2/T3 : burstable instances (up to a capacity)

  트래픽이 폭발하는 경우 CPU가 이에 맞게 뛰어난 퍼포먼스를 보여줌 이때 credit 을 소모하며 credit 을 다 사용하는 경우 CPU 성능은 다시 떨어짐. 이후 credit 이 다시 축척됨.

  - AWS has the concept of burstable instances (T2/T3 machines)

  - Burst means that overall, the instance has OK CPU performance

  - When the machine needs to process something unexpected, it can burst, and CPU can be very good.

  - If the machine bursts, it utilized "burst credits"

  - If all the credits are gone, the CPU becomes BAD

  - If the machine stops bursting, credits are accumulated over time

  - Burstable instances can be amazing to handle unexpected traffix and getting the insurance that it will be handled correctly

  If your instance consistently runs low on credit, you need to move to a different kind of non-burstable instance

TC/T3 - unlimited : umlimited burst

  credit 과 상관없이 CPU 가 항상 burst 에 대응함. 대신 추가적인 비용을 지불.

  - unlimited burst credit balance

  - You pay extra money if you go over your credit balance, but you don't lose in performance

  - Overall, it is a new offering, so be careful, costs could go high if you are not monitoring the health of your instances

[ 1. What is EC2? ]

EC2 인스턴스는 AWS에서 제공하는 대여형 가상머신

NAS 와 같은 역할을 하는 EBS, 로드밸런싱을 수행하는 ELB, 서버 트래픽에 따라 인스턴스 수를 증가/증감 시키는 ASG 등이 함께 사용된다

- EC2 is one of most popular of AWS offering

- It mainly consists in capability of :

  1) renting virtual machines(ec2)

  2) storing data on virtual drives(EBS)

  3) distributing load across machines(ELB)

  4) Scaling the services using an auto-scaling group(ASG)

* AMI (amazon machine image) : amazon linux2, redhat, Ubuntu, window ...

[ EC2 생성 후 접속 방법 (WINDOW10) ]

> ssh -i pem파일경로 EC2-user@EC2의공인IP

Permission denied(권한문제) 에러발생시 해결 방법(window 에서의 chmod 방법) :

techsoda.net/windows10-pem-file-permission-settings/

[ 2. Security Groups ]

EC2의 inbound/outbound 방화벽 정책으로 SG 를 한개 설정하여 여러개의 EC2 인스턴스에 동일하게 적용시킬 수 있다. (region 제약)

- Security Groups are the fundamental of network security in AWS

- They control how traffic is allowed into or out of our EC2 Machines

- acting as a "firewall" on EC2 instances

- They regulate :

  1) Access to Ports

  2) Authorised IP ranges (CIDR) - ipv4 and ipv6

  3) Control of inbound/outbound network

- can be attached to multiple EC2 instances

- locked down to a region /VPC combination

* if your application is not accessible (time out), then it's a security group issue (방화벽 문제)

* if your application gives a "connection refused" error, then it's an application error or it's not launched

- All inbound traffic is blocked by default

- All outbound traffic is authorised by default

[ # EC2 에 Apache 설치 ]

1) EC2 에 접속

2) > sudo su

    root 로 switch user

3) > yum update -y

force update machine

4) > yum install -y httpd.x86_64

아파치 설치

5) > systemctl start httpd.service

서비스 시작

6) > enable httpd.service

enabled across reboots

7) curl localhost:80

테스트

8) ec2publicip:80

외부에서 접속해보기 -> connection time out 발생

9) Security group 의 inbound 설정에 http 80 포트 추가

10) 재시도 성공 확인

security groups can communicate straight through to other instances

[ 3. Elastic IPs ]

고정된 공인 아이피, Elastic IP 설정시 EC2 인스턴스를 재기동해도 공인아이피가 바뀌는 현상이 나타나지 않는다

Elastic IP를 사용하기 보단, DNS (Route 53) 을 사용 하는게 구조적으로 낫다

- Elastic IP is a public IPv4 IP you own as long as you don't delete it

* if restart EC2 instance, it can change its public IP

- if you need to have a fixed public IP for your instance, you need an Elastic IP

- with an Elastic IP address, you can mask the failure of an instance or software by rapidly remapping the address to another instance in your account.

- you can only have 5 Elastic IP in your account (can increase if you ask AWS)

* try to avoid using Elastic IP :

  1) They often reflect poor architectural decisions

  2) Instead, use a random public IP and register a DNS name to it

[ 3. EC2 User Data ]

인스턴스 런칭시 실행되는 초기 스크립트로써 업데이트수행/프로그램설치 등을 EC2 런칭과 동시에 수행시키고자 할 때 사용한다 (AMI 를 사용하여 대체할 수 있다)

- It is possible to bootstrap our instances using an EC2 User data script 

- bootstrapping means launching commands when a machine starts

- That script is only run once at the instance first start (인스턴스 런칭과 동시에 스크립트 실행)

- EC2 user data is used to automate boot tasks such as:

  1) Installing updates

  2) Downloading common files from the internet 

* The EC2 User Data Script runs with the root user

* where to put/change user data

  생성시 : configure instance details step 의 advanced details 에서 설정

  생성후 : instance 우클릭 > instance settings > change user data

[ 4. EC2 Instance Launch Types ]

EC2 인스턴스는 아래와 같이 5가지 런치타입이 존재한다.

애플리케이션의 목적에 따라 런치타입을 바꾸어 비용절감을 할 수 있다.

1. On Demand Instances : short workload, predictable pricing

2. Reserved : (Minimum 1year)

  - Reserved Instances: long workloads

  - Convertible Reserved Instances: long workloads with flexible instances

  - Scheduled Reserved Instances: eg. every Thursday between 3 and 6 pm

3. Spot Instances : short workloads, for cheap, can lose instances (less reliable)

4. Dedicated Instances : no other customers will share your hardware

5. Dedicated Hosts : book an entire physical server, control instance placement

1. EC2 On Demand

필요시에만 사용, 비쌈

- Pay for what you use (billing per second, after the first minute)

- Has the highest cost but no upfront payment

- No long term commitment

- Recommended for short-term and un-interrupted workloads, where you can't predict how the application will behave.

2. EC2 Reserved Instances

일정 기간에 대한 선불제, 비교적 저렴

- Up to 75% discount compared to On-demand

- Pay upfront for what you use with long term commitment

- Reservation period can be 1 or 3 years

- Reserve a specific instance type

- Recommended for steady state useage applications(think database)

* Convertible Reserved Instance

  - can change the EC2 instance type

  - Up to 54% discount

* Scheduled Reserved Instances

  - launch within time window you reserve

  - When you require a fraction of day/week/month

3. EC2 Spot Instances

여유자원을 싸게 사용하는 방식으로 사용자가 최대 입찰 가격을 정해놓고 사용, 가격이 최대가격이상이 되면 중지

- Can get a discount of up to 90% compared to On-demand

- Instances that you can "lose" at any point of time if your max prices is less then the current spot price

- The Most cost-efficient instances in AWS

- Useful for workloads that are resilient(회복력있는/탄력적인) to failure

  eg. Batch jobs, Data analysis, Image processing

- Not great for critical jobs or databases

- Great combo : Reserved Instances for baseline + On-Demand & Spot for peeks

4. EC2 Dedicated Hosts

사용자 전용의 물리적 서버, 딮한 설정 가능

- Physical dedicated EC2 server for your use

- Full control of EC2 Instance placement

- Visibility into the underlying sockets/physical cores of the hardware

- Allocated for your account for a 3 year period reservation

- More expensive

- Useful for software that have complicated licensing model

  Or for companies that have strong regulatory or compliance needs

5. EC2 Dedicated Instances

계정에 귀속된 인스턴스

- Instances running on hardware that's dedicated to you

- May share hardware with other instances in same account

- No control over instance placement (can move hardware after Stop/Start)