Data transfer between instances in the same AZ is free. If the data crosses AZs, you're changed $0.01 per GB in both directions. This is for instances on a VPC. I think the pricing model is different for classic EC2.
There are some exceptions like all traffic between EC2 and ALBs being free.
Edit: Pricing is described at https://aws.amazon.com/ec2/pricing/on-demand/#Data_Transfer
I think everyone does something of this sort nowadays, that's why networking is ~free within data centers :)
> but an extra 1ms (say) between datacenters is generally bad for us and measurably reduces performance of some systems
That speaks to me. You will always be just the n-th client unless you own the cross-datacenter data links (i.e. have full autonomy on deciding the priority of the traffic). It's similar to the covid provisioning problems you had mentioned.
> One obvious example is that EC2 has "scheduled maintenance events" where they force you to reboot your box.
Yeah like others pointed out - that's just what "cloud" is, and is generally a good idea. You're supposed to handle a certain % of your machines going dark without a warning without violating any SLO (or even worse, certain % of your machines "pretending" they're up but actually being ridiculously slow for this or that reason; and don't even get me started on CPU/RAM bitflips).
It sounds to me that you run an extremely highly sensitive service, something for which paying for true ownership of the hardware just makes sense to remove those kinds of risks that most services don't care about. At the end of the day "cloud" is a shared resource, and no resource separation efforts will be 100% effective.
Nothing. You generally only pay for data going out of cloud providers. Not data going in or data being transferred within the same region.
> One obvious example is that EC2 has "scheduled maintenance events" where they force you to reboot your box. This would cost us a lot of money (mostly in dev time, to work around it).
You're not going to have a successful cloud experience unless you build your applications in a cloud suitable way. This means not all legacy applications are a good fit for the public cloud. Most companies really embracing the cloud are mitigating those risks by distributing workloads across multiple instances so you don't care if any one needs to be restarted, especially within a planned window.
> Also, multi-second network dropouts in big cloud datacenters are not uncommon (in my limited experience), but that would be really bad for us. We have millisecond-scale failover with 2x or 3x redundancy on important systems.
Are these inter-region network dropouts or between the internet and the cloud data center? You're not going to be relying on a public internet connection to the cloud for critical workloads.
All that being said, there are plenty of workloads which I don't think fit well in the cloud operating model. You may very well have one of them.
Right, we have not done this. We basically decided it was cheaper to keep doing the “old school” thing and not spend a bunch of dev time trying to do it in a way that supports arbitrary failure of N boxes. We just spent the money to make it unlikely our boxes or networks will fail, and if they do fail we may be sad (but it rarely happens, and has not yet happened in a catastrophic way).
> Are these inter-region network dropouts or between the internet and the cloud data center?
I’ve seen multi-second dropouts within a DC (cloud, not my current company), and multi-hour single-path failures between DCs (usually something like a fire or construction cutting a line). But all of our DCs have at least 2 physically independent routes to the internet, so it’s never taken us fully offline.
Our fault, I suppose -- but multi-az is prohibitively expensive if you need to run anything data heavy distributed.
> but multi-az is prohibitively expensive if you need to run anything data heavy distributed.
If you communicate between your AZs via ALBs, multi-az is effectively free. Our bill is so high because within our Kubernetes cluster, our mesh isn't locality aware; it randomly routes to any available pod. 2/3rds of our traffic crosses AZs.
It's nobody's fault that the billing structure at Amazon is so complicated and confusing.
Except Amazon's.
This is not true, AWS charges for all traffic cross AZ, so if you want a resilience within a region (which you mentioned in next paragraph) you will do a lot of that talking and this ends up a non trivial cost. You can do some optimization though by having your apps being aware of AZs they are on, but most places don't do that, more common are places that run everything from a single AZ.
It's interesting that you say this, because I think this just boils down to how you treat failures. Boxes will fail. It's inevitable, even if you run your own hardware.
We treat failure as an every-day event and have set up our systems so it doesn't matter. One box fails, an automated system notices and brings up another to replace it, while the remaining boxes take slightly more load for a few minutes.
Sure, that kind of failure tolerance doesn't come for free. But, again, you're going to have failures, no matter how much work you put into reliability (which also doesn't come for free!).
I believe I saw a slide that average lifespan of an EC2 instance at Netflix is 14 minutes.
I’m not necessarily saying cloud will work for your setup, but you can’t compare like that.
How much would it cost to move this across boxes in EC2? I actually don't know, that's not a rhetorical question. A lot of our servers have 10-40gbit links that we saturate for minutes/hours at a time, which I suspect would be expensive without the kind of topology optimization we do in our datacenters.
> Also surprised about latency
We've spent a surprising amount of money reducing latency :) We're not a high frequency trading firm or anything, but an extra 1ms (say) between datacenters is generally bad for us and measurably reduces performance of some systems.
> Reliability is "solved" at low levels
To whatever extent this may be true, it's certainly not true for cloud providers. One obvious example is that EC2 has "scheduled maintenance events" where they force you to reboot your box. This would cost us a lot of money (mostly in dev time, to work around it).
Also, multi-second network dropouts in big cloud datacenters are not uncommon (in my limited experience), but that would be really bad for us. We have millisecond-scale failover with 2x or 3x redundancy on important systems.