Hi Todd And Margo Chester!

 On 2011.09.19 at 18:03:08 -0700, Todd And Margo Chester wrote next:

> What I need help with is getting the optimum performance
> settings while converting over my old hard (virtual) drive.
> 
> This is what I have gathered from these parts as to the best
> settings:
> 
> - controller: virtio
> - kvm option: cache=none
> - qcow2 disk format with metadata preallocation
> - create your disk image with:
>      qemu-img create -f qcow2 -o \
>      size=40000000000,preallocation=metadata vdisk.img

If you don't need snapshots and such, you might get better performance
with LVM volumes for storing images, connected as "raw images". At least
that's only thing that I'm using in production and it works well.

For that, you create lvm volume of size of your hard drive, convert your
image to raw .img and write over lvm volume.

Storing images in filesystem is flexible, of course, but I believe it's
too risky on random power off or hang/reset and performance might be lower.

> And, I am vague how a *.qcow file/drive and a *.img file/drive
> relate.

.img is (usually) simple raw image, copy of hard disk, and qcow is
qemu-specific format with various features.
http://en.wikipedia.org/wiki/Qcow
http://wiki.qemu.org/download/qemu-doc.html#disk_005fimages

-- 

Vladimir