[virt-tools-list] virt-v2v question involving esx

[Richard W.M. Jones]

On Fri, Mar 18, 2011 at 08:40:31AM -0400, Kenneth Armstrong wrote:
> On Fri, Mar 18, 2011 at 8:06 AM, Dennis Jacobfeuerborn
> <dennisml at conversis.de> wrote:
> > On 03/18/2011 11:34 AM, Matthew Booth wrote:
> >>
> >> On 17/03/11 19:27, Richard W.M. Jones wrote:
> >>>
> >>> [Adding Matt]
> >>>
> >>> On Wed, Mar 16, 2011 at 02:59:40PM -0400, Kenneth Armstrong wrote:
> >>>>
> >>>> I have a vm on an esx server that I want to convert using virt-v2v. I
> >>>> know that it can connect to the esx server and copy the vmdk files
> >>>> down to do its conversion, but can I just use wget or something like
> >>>> that to copy the vmdk files down first, then use virt-v2v to convert
> >>>> the vm?
> >>>>
> >>>> The reason that I ask is that it would be better for me to do it this
> >>>> way, so that after I copy the vm files down, I can start the vm back
> >>>> up and let it be used while virt-v2v does the conversion on the copied
> >>>> image files. I like virt-v2v, but it takes a long time to do it's job
> >>>> with the copying.
> >>
> >> Are you saying that wget is substantially faster than virt-v2v's copying?
> >> I
> >> ask because virt-v2v uses the same http interface to retrieve the image.
> >> It
> >> actually streams and writes directly to the target destination, so unless
> >> the target destination is slow, I wouldn't expect this to save you a
> >> significant amount of time. The actual conversion process usually takes
> >> about a minute, so the copying time dominates almost completely.
> >>
> >> It is possible to do what you're asking, but it's a hassle. You'd need to
> >> obtain the storage files, create a local libvirt XML file which points to
> >> the local copies, then run virt-v2v using the libvirtxml input method.
> >
> > If the vmdk file is sparse then you might end up copying a lot less data
> > compared to a virt-v2v copy and since as you point out the copying is the
> > thing that dominates the migration time that can potentially be a big win.
> > It would be nice if virt-v2v had an option to not copy the block device but
> > instead the contents of a filesystem but that would probably make things
> > much more complicated since you'd have to support all kinds of filesystems,
> > LVM, potentially also copy UUID's etc., etc.
>
> Dennis is spot on.
> 
> If I copy down the file straight from the ESX server's web interface,
> it's quite quick.  However, when I try it through virt-v2v, the
> process takes hours downloading/converting the same file.
> 
> The vmdk file in question is a sparse disk.  So I assume that virt-v2v
> is expanding the disk out during the whole process?
> 
> -Kenny

You need to copy Matt in on these emails about virt-[pv]2v because
otherwise he won't see them.  In any case it's my understanding that
the latest version of virt-v2v handles sparse images properly.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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