Libguestfs - Dec 2018 - Re: v2v: -o rhv-upload: Upload via NBD

I posted this patch for vdsm, adding NBD APIs:
https://gerrit.ovirt.org/c/96079/

The main purpose of these APIs are enabling incremental restore, but they
also
enable a more efficient rhv-upload via NBD, and importing to thin disks,
which is
not possible with current solution.

The same idea can work for KubeVirt or other targets, minimizing specific
target code.

Here is how rhv-upload can work using NBD:

1. rhv-upload plugin separated to pre and post scripts

- pre - prepare disk and start image transfer
- post - finialize image transfer, create vm, etc.

2. rhr-upload-pre plugin create a transfer with transport="nbd"

POST /imagetransfers

<image_transfer>
    <disk id="123"/>
    <direction>upload</direction>
    <format>raw</format>
    <transport>nbd</transport>
</image_transfer>

Engine does not implement <transport> yet, but this should be an easy
change.

This will use the new NBD APIs to export the disk using NBD over unix
socket.
We can support later also NBD over TLS/PSK.

Engine will return NBD url in transfer_url:

   
<transfer_url>nbd:unix:/run/vdsm/nbd/<transfer_uuid>.sock</tansfer_url>

3. v2v use the trasfer_url to start qem-img with the NBD server:

    nbdkit (vddk) -> qemu-img convert -> qemu-nbd

Note that nbdkit is removed from the rhv side of the pipeline. This is
expected to
improve the throughput significantly, since imageio is not very good with
lot of
small requests generated by qemu-img.

4. rhv-upload-post script invoked to complete the transfer

What do you think?

Nir

On Sun, Dec 09, 2018 at 07:11:28PM +0200, Nir Soffer
wrote:
> I posted this patch for vdsm, adding NBD APIs:
> https://gerrit.ovirt.org/c/96079/
Great stuff.  What's the minimum version of oVirt which will have this
feature and what's the approximate date when we can assume most users
of oVirt will have this?

I don't have time now to implement the rest but I filed an RFE bug
referring back to your email:

https://bugzilla.redhat.com/show_bug.cgi?id=1657713

Rich.
> The main purpose of these APIs are enabling incremental restore, but they
> also
> enable a more efficient rhv-upload via NBD, and importing to thin disks,
> which is
> not possible with current solution.
> 
> The same idea can work for KubeVirt or other targets, minimizing specific
> target code.
> 
> Here is how rhv-upload can work using NBD:
> 
> 1. rhv-upload plugin separated to pre and post scripts
> 
> - pre - prepare disk and start image transfer
> - post - finialize image transfer, create vm, etc.
> 
> 2. rhr-upload-pre plugin create a transfer with transport="nbd"
> 
> POST /imagetransfers
> 
> <image_transfer>
>     <disk id="123"/>
>     <direction>upload</direction>
>     <format>raw</format>
>     <transport>nbd</transport>
> </image_transfer>
> 
> Engine does not implement <transport> yet, but this should be an easy
> change.
> 
> This will use the new NBD APIs to export the disk using NBD over unix
> socket.
> We can support later also NBD over TLS/PSK.
> 
> Engine will return NBD url in transfer_url:
> 
>    
<transfer_url>nbd:unix:/run/vdsm/nbd/<transfer_uuid>.sock</tansfer_url>
> 
> 3. v2v use the trasfer_url to start qem-img with the NBD server:
> 
>     nbdkit (vddk) -> qemu-img convert -> qemu-nbd
> 
> Note that nbdkit is removed from the rhv side of the pipeline. This is
> expected to
> improve the throughput significantly, since imageio is not very good with
> lot of
> small requests generated by qemu-img.
> 
> 4. rhv-upload-post script invoked to complete the transfer
> 
> What do you think?
> 
> Nir
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v

On Mon, Dec 10, 2018 at 12:29 PM Richard W.M. Jones <rjones@redhat.com>
wrote:
> On Sun, Dec 09, 2018 at 07:11:28PM +0200, Nir Soffer wrote:
> > I posted this patch for vdsm, adding NBD APIs:
> > https://gerrit.ovirt.org/c/96079/
>
> Great stuff.  What's the minimum version of oVirt which will have this
> feature and what's the approximate date when we can assume most users
> of oVirt will have this?
>
4.3 will have the vdsm APIs, I'm not sure about the release date.

The engine side transport support need to be discussed with
engine guys. Maybe we can get this also in 4.3, maybe in 4.3.z,
depending on how important is this feature to v2v.

I don't have time now to implement the rest but I filed an RFE
bug
> referring back to your email:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1657713

Thanks, good idea.

>
> Rich.
>
> > The main purpose of these APIs are enabling incremental restore, but
they
> > also
> > enable a more efficient rhv-upload via NBD, and importing to thin
disks,
> > which is
> > not possible with current solution.
> >
> > The same idea can work for KubeVirt or other targets, minimizing
specific
> > target code.
> >
> > Here is how rhv-upload can work using NBD:
> >
> > 1. rhv-upload plugin separated to pre and post scripts
> >
> > - pre - prepare disk and start image transfer
> > - post - finialize image transfer, create vm, etc.
> >
> > 2. rhr-upload-pre plugin create a transfer with
transport="nbd"
> >
> > POST /imagetransfers
> >
> > <image_transfer>
> >     <disk id="123"/>
> >     <direction>upload</direction>
> >     <format>raw</format>
> >     <transport>nbd</transport>
> > </image_transfer>
> >
> > Engine does not implement <transport> yet, but this should be an
easy
> > change.
> >
> > This will use the new NBD APIs to export the disk using NBD over unix
> > socket.
> > We can support later also NBD over TLS/PSK.
> >
> > Engine will return NBD url in transfer_url:
> >
> >
> 
<transfer_url>nbd:unix:/run/vdsm/nbd/<transfer_uuid>.sock</tansfer_url>
> >
> > 3. v2v use the trasfer_url to start qem-img with the NBD server:
> >
> >     nbdkit (vddk) -> qemu-img convert -> qemu-nbd
> >
> > Note that nbdkit is removed from the rhv side of the pipeline. This is
> > expected to
> > improve the throughput significantly, since imageio is not very good
with
> > lot of
> > small requests generated by qemu-img.
> >
> > 4. rhv-upload-post script invoked to complete the transfer
> >
> > What do you think?
> >
> > Nir
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> virt-p2v converts physical machines to virtual machines.  Boot with a
> live CD or over the network (PXE) and turn machines into KVM guests.
> http://libguestfs.org/virt-v2v
>