Re: [Xen-users] Maximum number of VMs per xen server

[mftahy <mofta7y@xxxxxxxxx>]

Hi Pandu,
thanks for your answer, really appreciate it.

About 70% of the VMs are paravirtualized Linux.
The remaining 30% are Windows with GPLPV drivers.

when reaching the 60th VM the CPU utilization will reach 2 - 3 on Dom0 which has access to 12 cores (so the utilization is approx 25%)
for Harddisk access I didn't check at that moment.

but if the issue is related tot he resources (IO or CPU) then even after I restart xend the problem should remain.
However when I restart xend (takes 30 min) the server can boot remaining VMs very fast (start slowing again when reaching above 50 new VMs)

so the issue looks like xend issue as it cannot start up more than 60 VMs without a long restart and after the restart I can start 60 VMs more and so on

Thanks


On 12-03-08 10:04 PM, Pandu Poluan wrote:

On Mar 9, 2012 2:13 AM, "moftah moftah" <mofta7y@xxxxxxxxx> wrote:
>
> Hi,
>
> It looks like I am having problems when I create more than 100 VM in
> one xen node.
>
> up to 60 VMs there is zero problems and between 60 and 100 problems start
>
> more than 100 the node becomes unstable.
>
> The node has tons of memory (more than 30 GB free)
> also the node has 16 cores so the processor isnt the issue here.
> is there any limitation in xen that prevent the system from serving
> more than 100 VMs ?
>

You're pushing 6 VMs per core, if the VMs are not paravirtualized, that's a huge load. There's also the question of I/O bottleneck.

After starting the 60th VM, i.e., when slowdowns begin, how's the processor and I/O load?

Rgds,

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