KVM vs XenServer
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@kuyaz said in KVM vs XenServer:
Hi all, for example my server has 16 core & 64gb RAM.
Just wondering, how many active VM I can run on those core actually? assuming for each VM I allocate 1GB, can I run 64 active VM with 1 virtual core each?
Can memory be shared also between VM?
When i said active, it is online but not in heavy usage.
It depends on the load, of course. Regarding the CPU, you can easily run 50+ VMs if they are idle. The CPU time is shared between the instance, so the overcommitment is very granular and efficient. Regarding the RAM, XenServer is not very good at RAM overcommitment by default; KVM instead can do a very nice job with similar instances, saving plenty of ram with KSM.
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@kuyaz said in KVM vs XenServer:
Hi all, for example my server has 16 core & 64gb RAM.
Just wondering, how many active VM I can run on those core actually? assuming for each VM I allocate 1GB, can I run 64 active VM with 1 virtual core each?
Can memory be shared also between VM?
When i said active, it is online but not in heavy usage.
I don't know what kind of processors your server has, and whether or not it's 2x 8-core CPUs, 1x 16-core CPU, or 4x 4-core CPUs.
But if it's a dual-CPU server with decent CPUs, you can easily run 50+ virtual machines at 1GB RAM each. Keep in mind your hypervisor will a small amount of RAM too.
It really depends on a lot of things. In one of my hypervisors, if I have a VM with 4x vCPUs assigned to it, and they are all at 100%, it is using up 2% of my hosts CPU power. That kinda tells me I can dish out 150+ vCPUs safely with them all running at 100%. That's never the case, so I'm sure I can safely assign well over 200 vCPUs. (so long as I have enough RAM for enough VMs it would take to use up 200 vCPUs)
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@kuyaz said in KVM vs XenServer:
Hi all, for example my server has 16 core & 64gb RAM.
Just wondering, how many active VM I can run on those core actually? assuming for each VM I allocate 1GB, can I run 64 active VM with 1 virtual core each?
You can run about 63. As long as you have enough RAM, you can run them. Over-provisioning CPUs will just cause systems to slow, not to be unable to run. RAM and storage are hard limits, CPU is not.
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@kuyaz said in KVM vs XenServer:
Can memory be shared also between VM?
That depends on the hypervisor. VMware ESXi can do this. It's an extremely limited feature and of little value. It's neat and good for things like VDI, typically, but not very useful for servers and there is a reason most platforms don't work towards adding it.
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@scottalanmiller said in KVM vs XenServer:
@kuyaz said in KVM vs XenServer:
Can memory be shared also between VM?
That depends on the hypervisor. VMware ESXi can do this. It's an extremely limited feature and of little value. It's neat and good for things like VDI, typically, but not very useful for servers and there is a reason most platforms don't work towards adding it.
I concur. For most workloads, it's more a pain than a solution.
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@olivier said in KVM vs XenServer:
@scottalanmiller said in KVM vs XenServer:
@kuyaz said in KVM vs XenServer:
Can memory be shared also between VM?
That depends on the hypervisor. VMware ESXi can do this. It's an extremely limited feature and of little value. It's neat and good for things like VDI, typically, but not very useful for servers and there is a reason most platforms don't work towards adding it.
I concur. For most workloads, it's more a pain than a solution.
yes I just realize that my question is stupid for the RAM part
