Do the capabilities of EC2 instances scale proportionately?

user_13139115 0
Viewed 54

Say I have three options:

Instance type vCPU Memory (GiB) Bandwidth (Gbps) Price
Small A B C D
Medium 2A 2B 2C 2D
Large 4A 4B 4C 4D

What are the implications of running 4 small instances vs 2 medium vs 1 large? Is one better or are they the same?

I am very new to all of this, thanks in advance.

amazon-web-services amazon-ec2
1 Answers

Your table is accurate within an Instance Type family. For example, m5.large, m5.xlarge and m5.2xlarge.

Some benefits of using multiple (smaller) instances are:

  • Distribute instances across multiple Availability Zones (different data centers) to avoid potential outage time (it is rare, but can happen)
  • If something goes wrong on a single instance, only a portion of your capacity is lost rather than losing all capacity
  • If your application is not capable of using multiple CPUs, then running threads on separate instances will perform better than running a single thread on a larger instance
  • Instances can be updated (eg installing a new version of software) individually, so only a portion of your total capacity is unavailable during the upgrade process, rather than it all being unavailable
  • You can test a newer version of your software on a single instance and monitor it closely to confirm that it is behaving as expected, rather than needing to roll-out changes all at once

The down-sides of using multiple instances are:

  • More overhead having to run operating systems on each instance (so less RAM and CPU is available to the application)
  • The application needs to be designed to run across multiple instances (typically in a stateless manner)
  • A Load Balancer is required to distribute the load (assuming you are running a web app)
user_1747770
Related