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t2 instances work great for many web services with daily load fluctuations if you view them as basically a billing mechanism. AWS originally offered a reserved-

t2 instances work great for many web services with daily load fluctuations if you view them as basically a billing mechanism. AWS originally offered a reserved-instance model where you didn't pay for instances that weren't running, but now that you pay for RI instance-hours regardless of usage, scaling down doesn't save you any money, so you either buy RIs to cover your peak usage (and waste money off-peak) or pay much higher on-demand prices some of the time. With t2's (which were introduced around the same time as the RI change), you can just run the right number of instances to keep your CPU Credit Balance above water (stockpiling credits off-peak) and buy RIs for them all, making them extremely cheap. And you can still auto-scale on the credit balance to avoid throttling in case of unexpected load.

blasdel 9y ago
I work on T2, and we just released a change that makes your CPUCreditBalance recover immediately instead of through the old complex 24h expiration model. There is now much less need to stockpile or manage your CPU credits: https://forums.aws.amazon.com/ann.jspa?annID=5196 https://forums.aws.amazon.com/ann.jspa?annID=5196 With T2 Standard auto-scaling based on the CPUCreditBalance can be a really bad idea, because the rate at which an account can launch T2s with an initial credit balance is limited. If your application has a bug that causes a health check to fail, the ASG can quickly burn through your launch credits by cycling the instances, and then it's possible for your health checks to keep failing because the later instances start with a CPUCreditBalance of zero. We just released T2 Unlimited in part to solve that. In this new version all instances start with a zero balance, but none are ever throttled and you can do a sustained burst immediately at launch: https://aws.amazon.com/blogs/aws/new-t2-unlimited-going-beyond-the-burst-with-high-performance/ https://aws.amazon.com/blogs/aws/new-t2-unlimited-going-beyo...
- dkersten 9y ago
  I'm a bit confused by the wording on the T2 unlimited post: > T2 Unlimited instances have the ability to borrow an entire day’s worth of future credits, allowing them to perform additional bursting. What does this mean? Specifically, what is meant by "borrow"? Do they have to be paid back? Does the next day then have fewer credits?
  - blasdel 9y ago
    Instead of ever being throttled your instance accumulates a "borrowed" CPUSurplusCreditBalance. If your CPU Utilization goes back below the threshold, the earned credits will pay down the surplus balance. If you terminate an instance with a nonzero CPUSurplusCreditBalance you'll be charged for the extra usage. We removed the direct relationship between credits and 24h cycles, so your current usage no longer affects tomorrow's balance: https://forums.aws.amazon.com/ann.jspa?annID=5196 https://forums.aws.amazon.com/ann.jspa?annID=5196
    - dkersten 9y ago
      Ahhh, I understand now, thanks.

blasdel 9y ago

I work on T2, and we just released a change that makes your CPUCreditBalance recover immediately instead of through the old complex 24h expiration model. There is now much less need to stockpile or manage your CPU credits: https://forums.aws.amazon.com/ann.jspa?annID=5196 https://forums.aws.amazon.com/ann.jspa?annID=5196 With T2 Standard auto-scaling based on the CPUCreditBalance can be a really bad idea, because the rate at which an account can launch T2s with an initial credit balance is limited. If your application has a bug that causes a health check to fail, the ASG can quickly burn through your launch credits by cycling the instances, and then it's possible for your health checks to keep failing because the later instances start with a CPUCreditBalance of zero. We just released T2 Unlimited in part to solve that. In this new version all instances start with a zero balance, but none are ever throttled and you can do a sustained burst immediately at launch: https://aws.amazon.com/blogs/aws/new-t2-unlimited-going-beyond-the-burst-with-high-performance/ https://aws.amazon.com/blogs/aws/new-t2-unlimited-going-beyo...

dkersten 9y ago
I'm a bit confused by the wording on the T2 unlimited post: > T2 Unlimited instances have the ability to borrow an entire day’s worth of future credits, allowing them to perform additional bursting. What does this mean? Specifically, what is meant by "borrow"? Do they have to be paid back? Does the next day then have fewer credits?
- blasdel 9y ago
  Instead of ever being throttled your instance accumulates a "borrowed" CPUSurplusCreditBalance. If your CPU Utilization goes back below the threshold, the earned credits will pay down the surplus balance. If you terminate an instance with a nonzero CPUSurplusCreditBalance you'll be charged for the extra usage. We removed the direct relationship between credits and 24h cycles, so your current usage no longer affects tomorrow's balance: https://forums.aws.amazon.com/ann.jspa?annID=5196 https://forums.aws.amazon.com/ann.jspa?annID=5196
  - dkersten 9y ago
    Ahhh, I understand now, thanks.