More machines means more power to cool them. Electricity bills are a big chunk of the cost of running a datacenter.
What issues? If your cloud architecture can't save power when demand is low, how can that be a positive?
> Go too far and you won't be able to also run a spot market in CPU instances like AWS does.
As I understand it, a spot market isn't ever an architectural goal, it's a way to exploit the practical realities of unused resources/capacity. If that necessity goes away, that'd be a win.
I see at least 3 possibilities:
1. The spot market is about filling temporarily-vacant VM slots on host physical machines
2. Additional physical machines must be kept online so that VMs can be quickly spun-up, and the spot market is about capitalising on this necessity (this is really a variation on Option 1)
3. The spot market is about deriving at least some revenue from the unutilised fraction of an always-on fleet, encouraging customers to run heavy jobs during times of low load on your cloud
I doubt Amazon's fleet is always-on -- I imagine they have fairly significant capacity in reserve to keep up with growth and spikes -- so I doubt it's Option 3. (This is a perfectly obvious question but I really can't find a definitive answer. Maybe my Google-fu is weak today.)
I wonder about live migration. I imagine there must be some brief interruption even there.
> Many VMs are run indefinitely, so whatever machine they’re on has to stay powered on
Amazon must be adequately motivated to find a way to power-down unused capacity. My guess is they have some kind of system to maximise this.
[0] https://www.theregister.co.uk/2012/12/20/aws_ec2_servers_ret...
Plus Xen has live migrate now, so I assume AWS’s frankenxen would have it as well.
There is indeed a brief interrupt, which is why I said they can’t be too aggressive with it.
Anyways, I’m sure Amazon does what it can to power down machines, I just think they’re stuck leaving much the data center running because they can’t kick off running VMs.
That doesn't sound right. A large number of weak computers, should be easier to cool. A cluster of smartphones can get by with passive cooling, but my laptop cannot.
Apart from cooling, I'm not an expert on this but I don't know that performance-per-watt has to improve as overall power increases. Going with my idea you'll need to power more motherboards, but they'll be less powerful motherboards. (The total number of CPU cores being powered remains the same. Same goes for RAM modules.)
Is that true? My phone gets quite hot if I run a taxing load on it for too long. My, perhaps poor, intuition tells me that phones can rely on passive cooling because of the burst nature of phone use. If you’re utilizing your smartphone cluster, I can imagine your fleet overheating.
iPhones survive long sessions of 3D gaming even when wrapped in protective plastic shells. If it was an issue, use a bigger passive heatsink than the one they cram into the smartphone form-factor. You could never do that with a server-grade CPU.
With a high-power CPU, the heat emissions are more concentrated than if we use many low-power CPUs.
The Raspberry Pi would have been a better example.
If cooling systems for machine rooms haven't caught up with modern systems that dissipate more heat, the direction you're thinking has merit. But I doubt there are serious limiting factors here, besides cost.
I think we agree, but I wasn't really thinking of power-savings as the real motivation here, I was thinking of security.
It seems likely we're going to see a steady steam of Meltdown/Spectre-like security concerns. We can have our cake and eat it -- isolation and all the CPU cleverness there is -- if the isolation between instances is done physically rather than with VMs.
There's clearly a market for weak, cheap, machines -- Amazon didn't originally offer a 'Nano' instance-type, but they do now.