[Xen-devel] Re: xen device migration

[Tej <bewith.tej@xxxxxxxxx>]

On Wed, Jul 30, 2008 at 12:16 AM, Mark Williamson
<mark.williamson@xxxxxxxxxxxx> wrote:
> On Tuesday 29 July 2008, you wrote:
>> Hi Mark
>>
>> I have some queries on Xen Migration setup
>>
>> VM resource are provided using NFS, iSCSI, AoE. After following the
>> below article http://archive.netbsd.se/?ml=xen-users&a=2007-12&t=6000155.
>> It suggests that we can migrate the disk and swap images using
>> external-device-migration.
>
> Heh, well it looks like I suggested that but I've never done it myself!  I
> believe it may be possible but it won't necessarily be efficient.
>
>> So it means that if we use the external-device-migrate script then all
>> the shared reosurce methos are not required ?
>
> In *principle*, if I was right about the external device migration scripts
> then it might eliminate the need for shared resources.  But unless you added
> some clever tricks then it would make live migration slower because of the
> need to copy the data across.  I think a good network-based disk solution
> will perform better since the disk and swap will be available immediately
> after the memory migration has been performed.
>
>
>> How do i use this method (to migrate the machine with device
>> migration)?
>
> Sorry, I don't know the details.  I guess you'd have to write a script that
> would do the device migration somehow (e.g. copying files across a network)
> and get the migration system to call it.  Sorry I can't be more specific.
>
>> Does xm migrate take care of using the device migration
>> scripts if shared resource (NFS, AoE etc) are not used.
>
> Not automatically, you'd need to tell it to use the migration scripts.  There
> might be some example scripts in the Xen repository you could look at but
> you'd probably have to do some customisation or possibly write your own.
>
>> or Am i missing something important.
>
> It's easy to set up Xend to automatically connect to nbd devices when a
> migration occurs.  Maybe you should consider that?
>
> In any case, you should take care to separate the migration traffic from the
> VM's network somehow so that VMs can't snoop on the data transmitted by
> migrations.

thanks for all your helpful pointers.

>
> Cheers,
> Mark

-Tej
>
> --
> Push Me Pull You - Distributed SCM tool (http://www.cl.cam.ac.uk/~maw48/pmpu/)
>

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