The answer to your question is "Yes".
Specifically, you if you do not place CPU caps on your service offerings,
you can over subscribe CPUs, so that if you have 4000 mHz on a server,
and combination of VMs will share that 4000 mHz, and when the physical
cpus are all maxed out, xenserver uses a fair scheduling algorithm to
limit each cpu to their fair share of CPU, but a Virtual CPU with 500 mHz
without a cap can use all the mHz available to it. Service Offerings with
a CPU cap are hard limited to the mHz in the service offering. In this
case, I'm not 100% sure what Cloudstack/Xenserver does from a
fair scheduling perspective, but I think you can still oversubscribe the
physical CPUs.
Regards,
Nik
Nik Martin
+1.251.243.0043 x1003
Relentless Reliability
On Fri, 11 Jan 2013, Wuming Zhang wrote:
Hi everyone, I'm wondering if I have understand Computer Offering correct.
Imagine I have one physical server that is 2Ghz with two cores. So 2 cores
and total 4000Mhz
If I want run 10 VM on it, should
CPU (in MHz): 400Mhz
# of CPU Cores: 1?
If I want to run 40 VM on it, should
CPU (in MHz): 100Mhz
# of CPU Cores: 1?
Is my assumption correct? Thanks in advance!
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Regards/Vänliga hälsningar/Zhi yi
Wuming Zhang
RHC{E,SS,A} & VCP
https://zhang.se - PGP KEY ID: 0xF4C7755C
