2 ms·

Didn't EC2 sell the cloud on the idea of being able to burst? Isn't it better to be able to do that for short periods without having to fire up a new server, c

Didn't EC2 sell the cloud on the idea of being able to burst? Isn't it better to be able to do that for short periods without having to fire up a new server, configure it, and pay for a whole hour? Your point is very valid from the point of view of benchmarking, but in the real world, I see bursting as a massive advantage. It feels like we need a better benchmark suite; like I/O test suites that can measure the burst rate and the sustained rate.

rbranson 17y ago
EC2 scales across instances, it does not burst CPU resources in a single instance. You can't depend on the "burstable CPU" to be available when you need it. It's a highly unreliable form of compute time. You just have to pray and hope no one else is using the same resources on the same physical machine, or you're SOL.
- justinsb 17y ago
  Right, I agree that scaling out is great. However, bursting is also a great feature; most loads are bursty (you're caching data and have a cache miss or timeout, you request an admin page which does a lot of computation.) All time-sharing involves statistical reasoning, even within your own application: all requests might be served from cache, or ten people might issue different cache-miss requests near-simultaneously. You just reason that under normal circumstances e.g. 80% of your requests will be served from cache, and that determines your typical load. Short-term bursting means that maybe you can size your machine closer to the mean load, rather than the 2 or 3 sigma load. So, I want _both_ bursting and scale-out :-) The benchmark is fair for measuring CPU bursting performance, but we do need a more comprehensive benchmark suite.
  - moe 17y ago
    Short-term bursting means that maybe you can size your machine closer to the mean load, rather than the 2 or 3 sigma load. No, it doesn't mean that. Because you can't rely on the resources to be available when you need them. The potential headroom may catch your first two spikes - and then crumble on the third. Would you buy a second-hand airbag for your car that only "usually works" but is a bit cheaper? Thought so.

rbranson 17y ago

EC2 scales across instances, it does not burst CPU resources in a single instance. You can't depend on the "burstable CPU" to be available when you need it. It's a highly unreliable form of compute time. You just have to pray and hope no one else is using the same resources on the same physical machine, or you're SOL.

justinsb 17y ago
Right, I agree that scaling out is great. However, bursting is also a great feature; most loads are bursty (you're caching data and have a cache miss or timeout, you request an admin page which does a lot of computation.) All time-sharing involves statistical reasoning, even within your own application: all requests might be served from cache, or ten people might issue different cache-miss requests near-simultaneously. You just reason that under normal circumstances e.g. 80% of your requests will be served from cache, and that determines your typical load. Short-term bursting means that maybe you can size your machine closer to the mean load, rather than the 2 or 3 sigma load. So, I want _both_ bursting and scale-out :-) The benchmark is fair for measuring CPU bursting performance, but we do need a more comprehensive benchmark suite.
- moe 17y ago
  Short-term bursting means that maybe you can size your machine closer to the mean load, rather than the 2 or 3 sigma load. No, it doesn't mean that. Because you can't rely on the resources to be available when you need them. The potential headroom may catch your first two spikes - and then crumble on the third. Would you buy a second-hand airbag for your car that only "usually works" but is a bit cheaper? Thought so.