Re: [Xen-API] XenServer/XCP replication (block changes tracking)

[Sébastien RICCIO <sr@xxxxxxxxxxxxxxx>]

About block changes tracking with vhdx, from qemu bugtracker:

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.


"Differencing images". That is what I guess is used by hyper-v to only 
replicate changed blocks of a virtual machine to another host


Cheers,
Sébastien

On 10.07.2013 20:39, srinivas jonn wrote:
> FYI
>
> vhdx support -- planned - no date yet, may need some influence within 
> the community
> http://xenorg.uservoice.com/forums/172169-xen-development/suggestions/3314266-xcp-support-vhdx-format-for-vdi
>
> ------------------------------------------------------------------------
> *From:* Sébastien RICCIO <sr@xxxxxxxxxxxxxxx>
> *To:* Dan Pollak <danpollak2@xxxxxxxxx>; "xen-api@xxxxxxxxxxxxx" 
> <xen-api@xxxxxxxxxxxxx>
> *Sent:* Wednesday, 10 July 2013 12:21 AM
> *Subject:* Re: [Xen-API] XenServer/XCP replication (block changes 
> tracking)
> Hi,
>
> Thanks for your reply. We already thought about using DRBD but if you 
> want to mirror a specific VM to a host and another VM on another 
> host., you'd have to set a drbd device at tapdisk level for each VM 
> disk and not on the entire SR and this look quite heavy to implement.
> I was thinking about a way to keep track of the changes at block level 
> somewhere between the VM and the vdi.
> I don't know how this is done on hyper-v, probably their new vhdx 
> format keep track of the changes. Xenserver actually badly lacks this 
> feature :(.
> Cheers,
> Sébastien
>
>
>
> On 09.07.2013 20:19, Dan Pollak wrote:
> > I am interested in this topic as well. I believe that most people are 
> > going to point you towards DRBD.
> > Regards,
> > Dan
> >
> >
> > On Tue, Jul 9, 2013 at 11:50 AM, Sébastien RICCIO <sr@xxxxxxxxxxxxxxx 
> > <mailto:sr@xxxxxxxxxxxxxxx>> wrote:
> >     Hi,
> >
> >     I would like to know if any of you know a solution to
> >     periodically mirror a running (or not) VM from one XenServer host
> >     to another, using some kind of block changes tracking on the
> >     vbd's (vdi's?).
> >
> >     I know there are softwares available like PHD Virtual, SEP or
> >     quartersoft alike that do this but:
> >
> >     1) they're quite expensive
> >     2) they need a dedicated appliance (vm) on each host to handle
> >     the mirroring
> >     3) and most important they don't use any block change tracking in
> >     order to read only the changed blocks when doing regulary mirrors.
> >
> >     This third point is really a pain as the whole vm image must be
> >     read each time in order to compare what has to be transfered.
> >
> >     Is there any existing solutions, or any plans to bring this
> >     feature to the next versions of XenServer.
> >
> >     I must admit that I was getting mad when I heard that Hyper-V 3
> >     (I want to avoid using it) has this feature  and having tried it
> >     myself  I must admit it works amazingly well.
> >
> >     Now that share-nothing migrations are available on XenServer
> >     (since 6.1 i think), the lack of this capability is the missing
> >     brick to make even more awesome it is already :)
> >
> >     Any suggestions?
> >
> >     Cheers,
> >     Sébastien
> >
> >
> >
> >
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