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It’s a lot easier and safer to scale hosts horizontally than vertically. You can predict the limits and behavior of each host, the VMs/processes on each host d
by cle 7y ago
It’s a lot easier and safer to scale hosts horizontally than vertically. You can predict the limits and behavior of each host, the VMs/processes on each host don’t need to deal with fundamental resources changing, etc. For services I own that are high availability, require GC tuning, etc., these hosts with dynamic resource adjustments (also T2/T3 in AWS) are a nightmare because the behavior can change at runtime under load, exactly when I want it to behave predictably.
- bullen 7y agoSure but: 1) Some things can't scale on more hosts, like say an action MMO with no sharding. 2) Scaling dynamically does not necessarily mean you have to do it unpredictably. Are you running them as unlimited or standard?
- cle 7y agoOh definitely there are valid use cases for these, was just sharing my experience with them for my use cases. We moved off of T2’s and back to C’s because of the unpredictable behavior under load. IIUC, T3s by default just bill you more instead of CPU throttling, which is a bit better for our use cases, but we haven’t tried them yet.
- bullen 7y agoAha, thanks for that very valuable information! T3 look cheaper and better than E2 then, my only problem is region placement where Iowa and Taiwan are more central than anything AWS offers (still no central US region!?). I'm in the MMO business, so very specific requirements.
- boulos 7y agoDisclosure: I work on Google Cloud. T3 is pretty different (even in unlimited mode) than E2. As an example, t3.xlarge (4 vCPU, 16 GB, $.167/hr, so $.042/hr/vCPU roughly) only has a baseline performance of 40% (so 1.6 vCPU). If you cross that threshold in unlimited mode you pay an additional $.05/vCPU/hr (so more than doubling your cost). By comparison an e2-standard-4 is $.134/hour even if you run it flat out. We take on the statistical multiplexing over the datacenter and move VMs around, instead of pushing it to you as an economic or performance-throttling risk when you need it most. If you want a burstable type, we do have an e2-{micro, small, medium} that only guarantees you 12.5%, 25% and 50% of your 2 guest-visible vCPUs. But that's more fit for dev workstations and so on.
- ti_ranger 7y ago> 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?
- boulos 7y agoSorry 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).
- _msw_ 7y agoDisclosure: 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.
- dodobirdlord 7y agoI 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.
- bullen 7y agoAre the T3 cores guaranteed to be on different physical cores? When are you building a central US region?
- 7y ago