AWS学习笔记（六）：Elastic IPs, Placement Groups, ENI, Hibernate, Nitro, Capacity Reservations

IPv4 allows for 3.7 billion different addresses in the public space

Elastic IPs - have a fixed public IP for your instance

• 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 (you can ask AWS to increase that).
• Overall, try to avoid using Elastic IP:
  • They often reflect poor architectural decisions
  • Instead, use a random public IP and register a DNS name to it
  • Or, as we'll see later, use a Load Balancer and don't use a public IP

Placement Groups

• Cluster - clusters instances into a low-latency group in a single Availability Zone
  

  • Pros: Great network (10 Gbps bandwidth between instances with Enhanced Networking enabled - recommended)
  • Cons: 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 - spreads instances across underlying hardware (max 7 instances per group per AZ)

  • Pros:
    • Can span across Availability Zones (AZ)
    • Reduced risk is simultaneous failure
    • EC2 Instances are on different physical hardware
  • Cons: 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 - spreads instances across many different partitions (which rely on different sets of racks) within an AZ. Scales to 100s of EC2 instances per group (Hadoop, Cassandra, Kafka)
  • Up to 7 partitions per AZ
  • Can span across multiple AZs in the same region
  • Up to 100s of EC2 instances
  • The instances in a partition do not share racks with the instances in the other partitions
  • A partition failure can affect many EC2 but won’t affect other partitions
  • EC2 instances get access to the partition information as metadata
  • Use cases: HDFS, HBase, Cassandra, Kafka

Elastic Network Interfaces (ENI)

• Logical component in a VPC that represents a virtual network card
• The ENI can have the following attributes:
  • Primary private IPv4, one or more secondary IPv4
  • One Elastic IP (IPv4) per private IPv4
  • One Public IPv4
  • One or more security groups
  • A MAC address
• You can create ENI independently and attach them on the fly (move them) on EC2 instances for failover
• Bound to a specific availability zone (AZ)

EC2 Hibernate

Under the hood: the RAM state is written to a file in the root EBS volume which must be encrypted
Use cases:

• long-running processing
• saving the RAM state
• services that take time to initialize

EC2 Hibernate – Good to know

• Supported instance families - C3, C4, C5, M3, M4, M5, R3, R4, and R5
• Instance RAM size - must be less than 150 GB
• Instance size - not supported for bare metal instances
• AMI: Amazon Linux 2, Linux AMI, Ubuntu & Windows…
• Root Volume: must be EBS, encrypted, not instance store, and large
• Available for On-Demand and Reserved Instances
• An instance cannot be hibernated more than 60 days

EC2 Nitro

Underlying Platform for the next generation of EC2 instances, Higher Speed EBS (Nitro is necessary for 64,000 EBS IOPS – max 32,000 on non-Nitro)

EC2 – Capacity Reservations

• Capacity Reservations ensure you have EC2 Capacity when needed
• Manual or planned end-date for the reservation
• No need for 1 or 3-year commitment
• Capacity access is immediate, you get billed as soon as it starts
• Specify:
  • The Availability Zone in which to reserve the capacity (only one)
  • The number of instances for which to reserve capacity
  • The instance attributes, including the instance type, tenancy, and platform/OS
  • Combine with Reserved Instances and Savings Plans to do cost saving