EC2 Associate

Private vs Public IP

• IPv4 allows for 3.7 billion different addresses in the public space
• Private IP
  • machine can only be identified on a private network only
  • unique across the private network
    • but, two different private networks can have the same IPs
  • connect to WWW using a NAT + internet gateway(proxy)
  • specified range of IPs 
• Public IP
  • machine can be identified on the internet
  • unique across the whole web
  • can be geo-located easily

Elastic IPs

• AWS가 제공하는 정적인 공인 IPv4 주소
• can attach it to one instance at a time
• IP 주소가 탄력적이면 한 인스턴스에서 다른 인스턴스로 빠르게 이동함으로써 인스턴스 혹은 소프트웨어의 오류를 마스킹할 수 있다 (드묾) 
• 계정 별 최대 5개
• 그러나 Elastic IP 사용은 피하는 것이 좋음
  • often reflect poor architectural decisions
  • use a random IP and register a DNS name to it
  • use a Load Balancer
• 소유한 IP가 중지된 인스턴스나 분리된 네트워크에 연결된 경우에도 시간당 요금이 부과

Placement Groups

• startegies for the group
  • Cluster
    • Great network
    • But, if the rack fails, all instances fails at the same time
    • Use Case :
      • Big Data job that needs to complete fast
      • Application that needs extremely low latency and high network throughput
  • Spread
    • Can span across Availability Zones
    • Reduce risk
    • Instances are on different physical hardware
    • Limited to 7 instances per AZ per placement group
    • Use Case :
      • Application that needs to maximize high availability 
      • Critical Applications where each instance must be isolated from failure from each other 
  • Partition
    • Up to 7 paritions for AZ
    • Can span across multiple AZ in the same regions
    • Up to 100s of EC2 instances
    • do not share racks with instances in different racks
    • A partition failure can affect many EC2 but won't affect other partitions
    • EC2 instances get access to the partition information as metadata
    • HDFS, HBase, Cassandra,Kafka

Elastic Network Interfaces (ENI)

• Logical component in a VPC that represents a virtual network card
• ENI attributes
  • Primary private IPv4, one or more
  • One Elastic IP per private IPv4
  • One public IPv4
  • One or more security groups
  • MAC address 
• Bound to a specific availability zone 

EC2 Hibernate (절전모드)

• The RAM state is preserved
• The instance boot is much faster
• The root EBS volume must be encrypted
• Use Case:
  • long running processing
  • saving the RAM state
  • services that take time to initialize 
• An instance can not be hibernated more than 60 days
• Available for On-Demand, Reserved and Spot Instances