클라우드 과정(MTC AZ-900) - 6주차

총소유비용(TCO)

1. CAPEX(자본 지출) : On-Premise 환경에 적용되는 단어
   -> Software license Fees + Implementation + Configuration + Training + Physical Security(도난, 파손 등) 
       + Hardware + IT Personal + Maintenance

2. OPEX(운용 지출) : Azure(Cloud) 환경에 적용되는 단어
   -> Subscription Fees + Implementation + Configuration + Training

==> 비교 시 클라우드 환경이 75%의 비용 절감이라는 이점을 가지고 있다.

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CAPEX = Capital Expenditure

• Physical infrastructure(Server, Storage, Network, Backup and Archive, Disaster Recovery, Datacenter, Technical Personal)에 대해 예측 후 먼저 비용 지불

OPEX = Operational Expenditure

• physical 부분과 관련된 비용은 들어가지 않음
• 장비사용에 대한 투자가 필요 없음
• 사용한 만큼만 비용 지불(Leasing Software and Customizing features, Training Employees in Cloud Services, Paying for Cloud Support, compute usage, storage usage)
• CAPEX에 비해 설치 시간이 적게 걸림

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<클라우드 아키텍처 용어>

• Availability(가용성) = Your ability to ensure a service remains available
  => Highly Available(HA)
• Scalability(확장성) = Your ability to grow rapidly or unimpeded
  => 서버와 서버 간의 확장성
• Elasticity(탄력성) = Your ability to shrink and grow to meet the demand
  => 시스템 전체의 확장성
• Fault Tolerance = Your ability to prevent a failure
  => 서버와 서버 사이의 실패점이 있느냐의 여부
• Disaster Recovery = Your ability to recover from a failure
  => 시스템 전체에 대한 백업을 하느냐

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1. High Availability (고가용성)

: Your ability for your service to remain available by ensuring there is no single point of failure and/or ensure a certain level of performance ( no single point of = 실패점이 하나가 아니다 = 이중화를 시켰다 )

1-1. Availability Zones

1-2. Azure Load Balancer

: A load balancer allows you to evenly distributte traffic to multiple servers in one or datacenter. If a datacenter or server becomes unavilable (unhealthy) the load balancer will route the traffic to only available datacenters with servers

2. High Scalability (높은 확장성)

: Your ability to increase your capacity based on the increasing demand of traffic, memory and computing power ( increase your capacity = 수요가 증가하였다 ) 
- Scaling Up -> Vertical Scaling (서버에 데이터가 있기 때문에 서버를 옆으로 늘릴 수 없어 위로 늘림)
- Scaling Out -> Horizonal Scaling (서버에 데이터가 없어서 옆으로 서버 늘림)

3. High Elasticity (고탄력성)

: Your ability to automatically increase or decrease your capacity based on the current demand of traffic, memory and computing power ( automatically = 클라우드에서 자동으로 조절)
- Scaling Out -> Add more servers of the same size
- Scaling In -> Removing more servers of the same size

4. High Durability (높은 내구성)

: Your ability to recover from a disaster and to prevent the loss of data Solutions that recover from a disaster is known as Disaster Recovery(DR)
- Do you have a backup?
- How fast can you restore that backup?
- Does your backup still work?
- How do you ensure current live data is not corrupt?