On Sat, May 2, 2015 at 1:33 AM, ToddAndMargo <[log in to unmask]> wrote:
> $ rpm -qa virt-manager
> virt-manager-0.9.0-28.el6.x86_64
>
> SL 6.6 x64
>
>
> Hi All,
>
> 1) In virt-manager, when I allocate a new a new hard drive,
>    I have a check-e-do that says "allocate entire disk now".
>    It then goes on the create a new hard drive for me.
>    Whether or not that check-e-do is checked, I get the
>    entire size.  Do I misunderstand that check box?  I was
>    thinking that unchecked meant that it was dynamically
>    expanding up to the maximum allocated.  Am I wrong?

It creates a "sparse" disk image. It doesn't actually use all the
blocks on the hypervisor's disk until they are written to to by the
guest image. This is a common way to overprovision disk on the
virtualization server, so that clients can have space available but
only consume what they each need.

> 2) When allocating a new hard drive, I have a choice of
>    IDE, and two Virtio Disks.  Do I need to have the
>    KVM guest additions (spice-guest-tools and virtio-win)
>    installed for Virtio disks to work?

Virtio is related to "para-virtualization", where the guest operating
system stops trying to emulate every single bit of hardware driver
management and forcing the virtualization server to read, interpret,
and then re-apply those controls to the *real* hardware drivers. This
is a case where the Google answers about virtio are pretty good.

> 3) What is the difference between and IDE and a Virtio
>    disk?  It the Virtio disk any faster?
>
> Many thanks,
> -T

It can be: the guest operating system has to support the drivers for
it, and not all older operating systems do.