On 05/28/2013 06:07 AM, Parakkal, Navin S wrote:

Hi, Can someone tell us what is the usual number of guests on a typical host in a production environment ? Has someone tested this ? What number does it scale to ? We have around 150 per host running fine.

It all depends on how beefy your hardware is, and how much you are willing to oversubscribe on memory to run your guests. It is quite easy to run more than one single-vcpu guest per processor, although you may need NUMA pinning to help that setup run efficiently; at least until you run into kernel limits of what KVM can do (for example, while you were able to run 150 guests, you might hit some sort of boundary at 256 or 512 guests according to how guests are represented in the kernel). Personally, I don't have a machine that beefy to tell you any hard numbers. If you really want to discuss scalability, you may be better off remembering that upstream is best effort only. If you need hard answers or guarantees for your particular setup, you may want to consider using an enterprise solution; for example, Red Hat has specific numbers of how many guests are supported on RHEL, along with benchmarks to back up their claims. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org