Solutions Architect

Section 6: EC2 - Solutions Architect Level

• Networking has both IPv4 and IPv6
• IPv4 is still the most common, but IPv6 is newer
• Almost running out of IPv4 addresses
• Private and public IP are different
• Companies typically have private networks, devices connect to internet gateway with private IP, which 'talks' to the internet through public IP
• Public IP's must be unique across entire web
• Public IP's can be geo-located easily
• Private IP are unique in private network
• Machines connect to WWW using a NAT + internet gateway (proxy)

Elastic IP

• If an instance needs a fixed IP, use elastic IP
• It is a public IPv4 you own
• Can be attached to one instance at a time
• You can have 5 in your account
• Try to avoid using this when possible

IP in EC2

• When stopped and restarted, an EC2 instance will get a new public IP
• Also has a private IP
• Use public IP for ssh, (we aren't in the same network)

Placement Groups

• Sometimes you want control over the EC2 Instance placement strategy
• When you create a placement group, you specify one of the following strategies for the group
  • Cluster: Instances in low-latency group in a single AZ
  • Spread: Instances across underlying hardware (max 7 instances per AZ) - for critical applications
  • Partition: Across many different partitions within AZ, Scales to 100s of EC2 instances per group

Cluster Placement Group

• Great network (10 GBps bandwidth with enhanced networking enabled)
• If the AZ fails, all instances will fail at same time
• Use case: Big data jobs (fast), applications which need low latency

Spread Placement Group

• Can span across AZ's, reduced risk of failure amongst all, on different physical hardware
• Limited to 7 instances per AZ per placement group
• Use case: Apps which need high availability, critical applications where failure isolation is critical

Partition Placement Group

• 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
• EC2 instances get access to the partition information as metadata

Elastic Network Interfaces (ENI)

• Logical VPC component, represent a virtual network card
• ENI can have these attributes:
  • Primary private IPv4, one or more secondary IPv4
  • One elastic IP per private IPv4 and 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

When we hibernate in instance:

• The in-memory (RAM) state is preserved
• The instance boot is much faster (OS is not stopped/restarted)
• Under the hood: the RAM state is written to a file in the root EBS volume
• The root EBS volume must be encrypted

Good for long-running processes, saving the RAM state, and services which take time to initialise