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How to sell vps and oversell to not affect users?
teochristian
Member
in Help
What is the math in overselling? How can I oversell a dedicated as to not affect the users?
Let's say I have a 40 core, 256GB ram server. How many 12 GB ram VPSs can I sell? (And how many cores per 12GB ram vps?)
Thanks!
Comments
Over 9000
at least 5, maybe 6 or even 7.
256/12=21 KVM VPS can be created. OVZ: as many you can till it brakes.
roughly:
give or take a few.
The clue is in your question, it begins with a D and ends in edicated
If KVM comes with ballooning, you can still oversell
What the heck is ballooning?
Same RAM usage policy as OpenVZ
If 2GB VM uses 512 MB RAM, then only 512 MB is reserved from the host. This allows you to put up 4x of the amount of VMs. And when your host runs out of RAM, due VMs starting to use more of their resources, the host will swap the extra RAM on NVMe SSD. Then hope ur customers wont notice a thing.
Theres an entire article for overcommiting on KVM https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualization_Administration_Guide/chap-Virtualization-Tips_and_tricks-Overcommitting_with_KVM.html
I know one scummy provider that has 1 NVMe disk reserved entirely for the overcommited swap/ram on their nodes. Theyre banned from here though.
Same logic as shared hosting. Goal is to make sure that most users aren't using VPS. If they are.. well that's what you sold them!
@AnthonySmith That’s some soggggy pizza.
You didn't mention anything about your drives or RAID setup. Disk IO will most likely be your limiting factor unless you're using SSDs in which case your storage limit will be your limiting factor.
How much disk space on the node?
How much disk space per VM?
And if he buys enough storage his budget is going to be his limiting factor.
Finding a node with 40 threads, even v2 E5's, 256GB RAM, and enough SSD storage to make it worth it, is going to be far and beyond what someone should be renting/leasing.
The OP's going to be stuck in a position where the node needs to be 80%+ just to meet bills, and that's at fairly up there pricing.
Francisco
What is the math? How can this not affect the users?> @KuJoe said:
I didn't mention. I have 2TB SSD. I would like to offer around 30GB per VM. Thank you!
That could be anything from a single drive to battery-backed hardware raid to ceph.
With my experience on OVH cloud with ceph, I would rather take the battery-packed hardware raid than ceph any day of the week.
What if I want the customized machine? can you deal in this way?
There's actually 2 questions in this.
the math in reasonable overselling is to have enough resources to satisfy the customers needs in a situation somewhere between normal load and peak load.
the other question - and the basis for your calculation - is what you can physically do.
Physically (as already someone mentioned) you can run 21 VMs at 12 GB each ... which also nicely matches the 40 cores (2 cores each) and the 2TB disk (100 GB each).
But it's more complex as diverse other factors are in the game. An example is networking. Another one is marketing. That kind of VMs would probably marketed in the upper mid range as "4vCores, 12 GB RAM, 100 GB disk". In that range you can't offer 50Mbit (translation: you'll need min. 4Gb Ethernet for that node).
This leads us to the next point, namely "what is overselling"? It can be two things, either reasonable usage of resources considering the fact that most customers don't use all their resources. For that your calculation depends on the type of customer you want to attract (which is largely defined by marketing/pricing) and may be typically a factor around 1.3 to 2.0. The other kind of overselling is, to put it straight, fucking your customers; for that I can't offer any advice.