Re: [Xen-API] vhdx support ?

[Dave Scott <Dave.Scott@xxxxxxxxxxxxx>]

Hi Mike, Sébastien,

> On 11/07/13 05:45, Sébastien RICCIO wrote:
> > I also googled around and found out that something was cooking at qemu
> > to support vhdx files:
> >
> > http://wiki.qemu.org/ChangeLog/1.5#Block_devices
> >
> >   * VHDX (MS Hyper-V) image format has initial read-only support.
> >     Dynamic and fixed sized disks are supported, but not differencing
> >     images (e.g. VHDX images with a backing file). Read-only is strictly
> >     enforced, and the 'readonly=on' option must be used for any VHDX
> images.
> >
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=879234
> >
> > Maybe I'm wrong but it seems that upstream qemu will be used in a not
> > so far distant future to support Ceph filesystem aswell
> >
> > http://www.xenserver.org/component/easyblog/entry/tech-preview-of-
> xens
> > erver-libvirt-ceph.html?Itemid=179
> >
> > Maybe a dream come true ? :)
> >
> > Cheers,
> > Sébastien
> 
> Getting upstream qemu into XenServer is on the work list for the next three
> months, so it's possible this will come soon to xapi.

Indeed. Once we've done the work to incorporate 'libxl' and then switched to 
xen 4.3, we'll probably be using the upstream qemu by default. In my prototype, 
Ceph is working but the code is experimental.

> VHDX support won't just
> come free with qemu, though; it'll take a lot of work in the storage
> managers and supporting infrastructure. I'm really not sure when VHDX
> support is going to make it onto the roadmap, but I know it's on the storage
> team's minds.

I think there are multiple ways of handling vhdx. As soon as qemu supports it 
we should be able to use it in simple configurations. However it would probably 
be lots of work to make it fully functional with online coalesce, IntelliCache 
support etc. However many users (for example in the cloud) might not really 
care about these features. So we could choose to add vhdx, and gradually 
support it in more and more configurations. I'm very keen to make it possible 
to play with it asp and see how well it works...

BTW the first step to making it work in XenServer is to make it work on vanilla 
xen 4.3, with upstream qemu and 'xl'. If someone could try that and report back 
it would be very helpful!

Cheers,
Dave

> 
> Mike
> 
> 
> >
> >
> > On 11.07.2013 05:57, srinivas jonn wrote:
> >> Mike,
> >>
> >> this is an existing  VHDX implementation (opensource) for XenServer
> >> storage team to consider:
> >>
> >>
> http://discutils.codeplex.com/SourceControl/latest#src/Vhdx/DiskImageFil
> e.cs
> >>
> >>
> >> "DiscUtils is a .NET library to read and write ISO files and Virtual
> >> Machine disk files (VHD, VDI, XVA, VMDK, etc). DiscUtils is developed
> >> in C# with no native code (or P/Invoke)"
> >>
> >> ------------------------------------------------------------------------
> >> *From:* Sébastien Riccio <sr@xxxxxxxxxxxxxxx>
> >> *To:* Mike McClurg <mike.mcclurg@xxxxxxxxxx>
> >> *Cc:* "xen-api@xxxxxxxxxxxxxxxxxxx" <xen-api@xxxxxxxxxxxxxxxxxxx>
> >> *Sent:* Monday, 11 June 2012 3:10 PM
> >> *Subject:* Re: [Xen-API] vhdx support ?
> >>
> >> Hi Mike,
> >>
> >> Thanks for your reply. Well yes vhdx is very new, it is not yet released
> >> as it's part of the windows 8 server hyper-v layer which is currently
> >> in beta as far as I know. But still this is very interesting and I am a
> >> bit worried that windows 8's hyper-v is going to take a big step ahead
> >> of other virtualisations solutions.
> >> I love Xen and XCP but I must admit that they've implemented really nice
> >> features...
> >>
> >> I don't think there is any vhdx open source implementation yet. I
> >> thought there was a partnership between citrix and microsoft, but maybe
> >> I'm wrong.
> >>
> >> Still there is the technical specification document available on ms site:
> >>
> >> http://www.microsoft.com/en-us/download/details.aspx?id=29681
> >>
> >> If your storage team want to take a look at it.
> >>
> >> Cheers,
> >> Sébastien
> >>
> >>
> >> On 07.06.2012 10:35, Mike McClurg wrote:
> >> > On 01/06/12 23:29, Sébastien Riccio wrote:
> >> >> Hi,
> >> >>
> >> >> I don't know where this question should be posted, but I'll try here.
> >> >>
> >> >> Is there any plan for XenServer/XCP/Kronos to support the vhdx
> format
> >> >> that should get rid of the 2tb limit for a single volume ?
> >> >>
> >> >> As seen somewhere on the interweb:
> >> >>
> >> >> Now with VHDX Microsoft kills this limitations and brings some other
> >> >> improvements:
> >> >>
> >> >>  * Supports up to 16TB size
> >> >>  * Supports larger block file size
> >> >>  * improved performance
> >> >>  * improved corruption resistance
> >> >
> >> > I just spoke to our storage team dev lead about this. The short answer
> >> > is that we want to support it, but we don't have any plans for it in
> >> > the short term.
> >> >
> >> > The real benefits we would get out of VHDX would be breaking the 2TB
> >> > limit, and potential performance improvements. Modifying our current
> >> > VHD implementation might let us do that, without actually
> implementing
> >> > VHDX. Perhaps QCOW images might allow disks bigger than 2TB, but I
> >> > don't really know.
> >> >
> >> > The biggest issue with implementing VHDX is that we don't know of any
> >> > existing, open-source implementation of it, which means that we
> would
> >> > have to invest a lot of time to write our own from scratch. If anyone
> >> > knows of any existing VHDX implementations that we can use, I'm sure
> >> > the storage team would like to hear about it!
> >> >
> >> > Mike
> >> >
> >>
> >>
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> >>
> >
> 
> 
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