what is t2 unlimited in AWS EC2 t2 instance type?
AWS recently introduced “t2 unlimited concept” in t2 series. The advantage in t2 series is “burst capability” when comparing with other instance type.So whenever load comes it can burst the CPU to handle the load . It will utilize the cpu credit to provide high performance . But normally when you burst all the cpu credit, again the instance has to run baseline performance.Now with t2 unlimited feature you can still get burst performance .Lets see how it works.
- A T2 Unlimited instance can sustain high CPU performance for any period of time whenever required
- his enables you to enjoy the low T2 instance hourly price for a wide variety of general-purpose applications, and ensures that your instances are never held to the baseline performance.
- T2 Standard is the default configuration; if you do not enable T2 Unlimited, your T2 instance launches as Standard.
- You can switch from Standard to Unlimited, and from Unlimited to Standard at any time on a running or stopped instance.
- T2 Unlimited instances do not receive launch credits.
How Does T2 Unlimited Work?
When a T2 Unlimited instance has exhausted its CPU credit balance, it can consume surpluscredits to burst beyond the baseline. Surplus credits are tracked by the CloudWatch metric CPUSurplusCreditBalance. When an instance’s CPU utilization falls below the baseline, the credits that it earns are used to pay down (or reduce) the surplus credits it consumed earlier. The ability to earn and pay down credits enables Amazon EC2 to average the CPU utilization of an instance over a 24-hour period.
When is a T2 Unlimited Instance Charged?
If the average CPU utilization of the instance is at or below the baseline, the instance incurs no additional charges. However, if CPU utilization stays above the baseline and the instance does not pay down the surplus credits it has consumed, the surplus credits are charged at $0.05 per vCPU-hour.
So its almost like taking a loan and re-pay based on instance hourly earning ,but here time is just 24hr. If your instance earning is less and if you used more surplas cpu credit , for additional usage you have to pay little bit .
Overall t2 series becoming good choice when for regular workloads.
For detailed information :
http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/t2-unlimited.html#describe-t2