Neil Garthwaite wrote:> Hi,
>
> I''m trying to understand how a Solaris domU accesses either a
file-back
> or device-backed VBD images. By "accesses" I simply mean how a
VBD
> appears to the domU.
>
> Looking at http://opensolaris.org/os/community/xen/docs/specs.html
>
> "...
> DomU Disk Space Requirements
>
> Solaris supports both file-backed and device-backed VBD images.
> File-backed images are files containing the UFS file system image.
> File-backed images are accessed by mounting the file using the loopback
> file driver described in the lofi(7D) man page. Device-backed images can
> be stored in a disk partition or a Solaris Volume Manager device.
> Solaris Volume Manager soft partitions are the recommended method for
> storing domU images for the flexibility and performance advantages they
> have over physical disk partitions and file-backed images.
> ..."
>
> Q1. My understanding is that when running virt-install using -l
> <path>.iso that lofi will be used to mount the iso image used by
> virt-install. However how is the file-backed VBD image say
> /export/solarisPV/root.img made available to the guest domain. I''m
> interested if lofi is somehow used after the file-backed VBD is created,
> i.e. once the install is complete does domO somehow export via lofi the
> VBD image to the domU.
Yes, the current code uses lofi for disk files.
> Q2. As a follow on to Q1. how is a device-backed VBD image made
> available to the domU.
Not sure what your asking here.
> Looking at http://opensolaris.org/os/community/xen/docs/developers/
>
> "...
> In a paravirtualized domU, each driver has a "front end," which
is
> present within the domU, and a "back end," which runs in dom0.
These are
> referred to as PV drivers. The front end driver takes standard requests
> from Solaris and forwards them to the back end driver. The back end
> driver executes the request on the physical hardware and passes any
> result back to the front end driver, which then notifies Solaris of the
> request''s completion. Since the driver is explicitly hypervisor
aware,
> it is able to work with the hypervisor and the back end driver to
> deliver much better performance than a driver in a fully virtualized
> environment.
> ..."
>
> Q3. Is lofi used by these PV drivers?
lofi is only used for disk files, e.g. .iso and
.img files... It is not used for svm volumes,
raw disks, raw disk slices, or zvols.
lofi should be removed in the path within the
next couple of months.
MRJ