[libvirt-users] sharing read-only LOCAL disks among KVM guests

[Henrik Ahlgren]

On Fri, Sep 21, 2012 at 09:22:24PM +1000, Amos Shapira wrote:
> 2. Maintenance - if I get to share the common disk image among all of them
> then I only need to install/update it once instead of once for each KVM
> guest (we already use Puppet but it doesn't mean it comes for free).

How do you plan on upgrading the read-only VMs after the initial
installation, or are they short-lived and frequently recreated from
scratch using a fresh image? Read-only, shared /usr between machines
is a nice idea in theory, but at least the modern linux distros'
package management tend not to support it that well in practice.

IMHO using a QCOW2 backing files as base templates works pretty well
and gives you similar disk space savings, at least initially. And
KSM does the same with RAM.