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Is a VPS (non-dedicated) expected to have noticeable pauses?
I have a real-time server program which sends updates to each client every 100 ms. CPU load is rather minimal, so I don't think a dedicated server is necessary. However, it is important that the updates are received at a more-or-less constant rate by the clients.
Since non-dedicated VPSes share CPU time with other virtual machines, is a normal non-dedicated KVM VPS expected to be able to send the updates every 100 ms (barring maybe 10-30 ms of inconsistency), or will I have spans of 200ms+ without any data sent (due to the host pausing my VM to let other machines run)?
In other words, would I see 100ms+ intermittent pauses on my VM, or would the pauses be small enough so that it would seem like my server is just running on a slower machine?
Comments
What is the iowait on that system like
You'll get occasional pauses like that from network randomness all by itself. There's no way you should run any type of hard real time process over the internet. That said, a pure SSD vps will give you better consistency than one with a hard drive, and avoiding disk i/o in your sending thread helps. If you can stand occasional misses you should be ok.
If this is for media streaming, use buffering. If it's VOIP, try to put your server very close to the endpoints. Your calls will have occasional dropouts and you've probably experienced them on VOIP calls yourself.
A VPS runs in a shared environment split among you don't know how many users, so the only logical conclusion is that it will be 100% stable down to the last millisecond, never have any kind of hiccup or lag. And if it ever does you just come to LET and post how it's oversold scam and that you demand a refound.
There is no file I/O at all once my server is up and running. Processing of each update is done entirely in RAM.
It's for a multiplayer game. I'm just wondering if I should be concerned about whether KVM pausing my VM would have noticeable impact on the updates. Like maybe KVM is programmed to switch VMs every 50 ms or something, similar to the way an OS pauses threads to let other threads run.
I'd say it is not so much important if you have openvz, kvm or dedi. Network itself has much higher impact on latency. And multiplayer game must be aware of it...
100% of the time 24x7/365? nope, because in simple terms, shit happens.
99% of the time, yep probably.
Not sure what exactly it is you are doing, but it sounds like it has a major weakness built in to its foundation if it was intended to run over a WAN to begin with.
It's like those io games, so by definition, they have to run online on the web.
Seems like the consensus here is that a non-dedicated VPS would be able to do what I want, and I won't have spurious pauses induced by the KVM virtualizer.
Regarding network latency, yeah it is a problem which probably could be minimized by having a few servers in various locations around the world.
Thanks for your help!