Comment 6 for bug 828357

On Mon, Aug 22, 2011 at 01:13:54PM -0000, Scott Moser wrote:
> A couple more things. I suspect volumes in windows instances are not
> formated with ext3. I actually have never looked. If you'd like I
> *can* dig that up, but the primary point would be that I suspect
> filesystems type is instance-OS specific (at least to the point of
> windows/linux).

Okay, os_type is passed to libvirt driver. So we can choose which
file system to use. So which file system should be used?

os_type
   'linux' => mkfs.ext3
              mkfs.ext3 -L <volume-label>

   'windows' => mkfs.vfat
                do we want to use
                -n <volume-name>
                -i <volume-id>

                or

                mkfs.ntfs
                do we want to use
                --label STRING
                --fast: perform a quick format

   other os => We don't know. (Solaris, BSD* ...)
                leave it uninitialized or make it user configurable?

> The other thing is that mkfs on a large volume will take quite a while,
> so you'd most definitely want to consider that. Maybe cache the volume
> after mkfs was done?

Fortunately the files is cached in /var/lib/nova/instance/_base/ as you
described.
If ext4 could be used, uninit_bg option could be used. It reduces mkfs
time much.