Historic Notes

• These notes were originally written 2018

Dynamic EC2 instances:

• To find which instances belong to which EBS environments, go to EBS | Health, and find instance Id
• These are spun up on demand by EBS load balancer
• You can see a log of when they are created and deleted in EBS | Events

IP addresses

• To see IP address, select Instances on the left, select an, then lower right see “IPv4 Public IP”
• To find out which instances are being spawned by a particular EBS config:
  • Select the EBS project
  • Click Health on the left hand side
  • You will see an instance Id there – you can map this back to EC2

Volumes vs Instances:

• Sometimes when you look at EC2 you may see, for instance, 27 instances but 33 volumes. Even if some instances have been terminated, that still won’t explain the shortfall.
• There are always more volumes than instances
• It’s about memory. You can increase the hard disk effectively – so some instances might have more than one volume

EC2 Instance Sizes

• eg t1.micro or t2.small. You might want to change an instance size, eg if an instance is crashing when running npm install, which could be caused by a lack of space to accommodate downloaded packages.

Terminated EC2 instances

• They’re terminated because they were spun up by the load balancer, and are no longer needed
• Check EBS for health checks
• You’ll see more of them if you are prone to brief periods of high load – new instances get spun up in response to load
• They remain in terminated state for a while so you can look at them, but then after a while they disappear

High availability

• Separate instances are in different geographical areas.