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Comment by ti_ranger | Hacker News Reader

> We take on the statistical multiplexing over the datacenter and move VMs around

You're implying here that EC2 doesn't do this.

On what basis?

Sorry if I was unclear. In unlimited mode, if you sustain greater than your baseline percentage, you pay for it (the key point of the sentence you’re quoting is that we take on the risk). One reason for this happens to be because AWS doesn’t do migration (yet?), but instead does an awesome job of doing in-place upgrades (see their talks on Nitro, for example).

Disclosure: I work for AWS.

We have many tools in our toolbox at our disposal: non-disruptive in-service updates moves live migration from a "must have to operate compute cloud service at all" to "helpful in some scenarios when the workload and/or situation warrants the impact to performance during precopy / potential post-copy phases."

But I would not assume that EC2 does not have that particular tool in the "fully production, and used" toolbox.

I have my doubts, in the past I've received decom-notifications that EC2 was going to be shutting down my instances in the near future due to underlying hardware failure (very helpful, since I was in the middle of triaging why the instance was behaving strangely). Seems like a poor customer experience to reap running instances if live migration is on the table.

Are the T3 cores guaranteed to be on different physical cores?

When are you building a central US region?

Disclosure: I work for AWS

T3 instances provide hyperthreadded vCPUs to EC2 instances, and the Nitro Hypervisor uses a core based scheduler (coscheduler) to ensure that cores are never shared between two EC2 instances.

Upstream Linux kernel changes that are based on some of the changes in the Nitro Hypervisor were posted to lkml in 2018: https://lwn.net/Articles/764482/

I hope to see the GCE team contributing more to the ongoing discussion on core based scheduling!

That doesn't really answer my question, if I have a t3-micro (which cores do not fill an entire physical core, so they are shared with others) am I guaranteed both of the cores for the instance are running on separate physical cores so that my two cores don't share one physical core?

This in order to allow for my server to continue operation if the steal rate of one core goes through the roof because some other instances running on my shared physical core are taking too many resources unexpectedly.

And how does Amazon explain still not having a central region in the US? I mean the multiplayer share of your revenues must be at least 10% by now?

I just managed to get a IONOS instance running in Kansas City (same distance from east/west-coasts) for low-and-behold 1€/month with unlimited data (18GB SSD and 512MB RAM). How is AWS going to compete with that?

A t3.micro has two vCPUs, where each vCPU is backed by a hyperthread of a physical core. Because the scheduler used by the Nitro Hypervisor core based scheduling (see [1]), the two vCPUs will always map to the two threads of a physical core. You will not run on two separate physical cores are the same time if you have only 2 vCPUs allocated to your T3 instance.

The scheduler can move where your vCPUs run based on available resources.

I can try to explain virtual machine CPU scheduling, but I can't explain when or where AWS will build new regions that have not been announced. :-)

[1] https://lwn.net/ml/linux-kernel/20180907214047.26914-1-jscho...

Are the E2 cores guaranteed to be on different physical cores?

Every search result I can see says that EC2 doesn't do live migration. You can try to balance things but you can only do so much if you can only move a VM when it happens to reboot by itself. (And there's no evidence I can find that they even do that.)

Disclosure: I work for AWS on EC2

EC2 instances that have no local storage state can move between hosts in response to events like reboots.

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