10:40 a.m.
It turns out that the general migration strategy I defined[1] in
reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
sufficient to support KVM migration.
The problem is that the destination needs to start qemu-kvm with
pretty much the exact same configuration / command line parameters as
were used at the source[2]. eg. If the source qemu-kvm has 512 MB of
RAM, then the destination had better have exactly 512 MB of RAM also.
(This is not the same as Xen where the migration protocol itself
carries this information between the two xend daemons).
We can modify the Prepare step to pass this information -- I'm
suggesting that we just pass the domain XML of the source domain.
Thus the Prepare step would change from:
static int
qemudDomainMigratePrepare (virConnectPtr dconn,
char **cookie,
int *cookielen,
const char *uri_in,
char **uri_out,
unsigned long flags,
const char *dname,
unsigned long resource)
to:
static int
qemudDomainMigratePreparev2 (virConnectPtr dconn,
char **cookie,
int *cookielen,
const char *uri_in,
char **uri_out,
+ const char *dom_xml,
unsigned long flags,
const char *dname,
unsigned long resource)
As hinted there, we also need a new version of the migration protocol,
and a new remote call (Preparev2).
So questions:
(a) Does anyone have any objections?
(b) Does anyone see a simpler way to do this?
(c) Since we're adding a second version of the protocol, does anyone
want anything else added?
(d) Will the domain XML alone be sufficient to recreate the exact
qemu command line? (Seems to be the case, and in fact KVM suspend/
restore support seems to implicitly rely on this too).
Rich.
Notes:
[1] https://www.redhat.com/archives/libvir-list/2007-July/msg00357.html
and https://www.redhat.com/archives/libvir-list/2007-July/msg00304.html
[2]
http://kvm.qumranet.com/kvmwiki/Migration#head-71900dbcf45d8ac81649fe4f03...
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
virt-top is 'top' for virtual machines. Tiny program with many
powerful monitoring features, net stats, disk stats, logging, etc.
http://et.redhat.com/~rjones/virt-top
10:58 a.m.
On Mon, Apr 07, 2008 at 04:40:41PM +0100, Richard W.M. Jones wrote:
It turns out that the general migration strategy I defined[1] in
reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
sufficient to support KVM migration.
The problem is that the destination needs to start qemu-kvm with
pretty much the exact same configuration / command line parameters as
were used at the source[2]. eg. If the source qemu-kvm has 512 MB of
RAM, then the destination had better have exactly 512 MB of RAM also.
(This is not the same as Xen where the migration protocol itself
carries this information between the two xend daemons).
We can modify the Prepare step to pass this information -- I'm
suggesting that we just pass the domain XML of the source domain.
Thus the Prepare step would change from:
static int
qemudDomainMigratePrepare (virConnectPtr dconn,
char **cookie,
int *cookielen,
const char *uri_in,
char **uri_out,
unsigned long flags,
const char *dname,
unsigned long resource)
to:
static int
qemudDomainMigratePreparev2 (virConnectPtr dconn,
char **cookie,
int *cookielen,
const char *uri_in,
char **uri_out,
+ const char *dom_xml,
unsigned long flags,
const char *dname,
unsigned long resource)
As hinted there, we also need a new version of the migration protocol,
and a new remote call (Preparev2).
So questions:
(a) Does anyone have any objections?
Not really but i wonder if we can't hack some backward compatible
implementation. Basically if you pass the XML you don't need to pass the
dname domain name. And on an older implementation if receiving XML
on a domain name if properly checked you should error out early on
the receiving end allowing to retry the Prepare step with just the name.
(b) Does anyone see a simpler way to do this?
Actually passing the XML is the simplest since you send all the informations
What concerns me is to try to keep old and new versions to still communicate
okay. maybe the Preparev2/Prepare allows already the do this when falling
back if the receiving end has no Preparev2.
(c) Since we're adding a second version of the protocol, does
anyone
want anything else added?
Never need a v3 ;-)
(d) Will the domain XML alone be sufficient to recreate the exact
qemu command line? (Seems to be the case, and in fact KVM suspend/
restore support seems to implicitly rely on this too).
Daniel
--
Red Hat Virtualization group http://redhat.com/virtualization/
Daniel Veillard | virtualization library http://libvirt.org/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
11:53 a.m.
On Mon, Apr 07, 2008 at 11:58:24AM -0400, Daniel Veillard wrote:
> static int
> qemudDomainMigratePreparev2 (virConnectPtr dconn,
> char **cookie,
> int *cookielen,
> const char *uri_in,
> char **uri_out,
> + const char *dom_xml,
> unsigned long flags,
> const char *dname,
> unsigned long resource)
>
> As hinted there, we also need a new version of the migration protocol,
> and a new remote call (Preparev2).
>
> So questions:
>
> (a) Does anyone have any objections?
Not really but i wonder if we can't hack some backward compatible
implementation. Basically if you pass the XML you don't need to pass the
dname domain name. And on an older implementation if receiving XML
on a domain name if properly checked you should error out early on
the receiving end allowing to retry the Prepare step with just the name.
The dname is used when you want to rename the domain during the
migration (if indeed this is supported - it isn't in Xen, it will be
in KVM).
So in most cases dname is actually NULL.
However ... the current Xen driver turns out to ignore the dname
during Prepare, but later on errors out if dname != NULL in the
Perform step.
Could that behaviour be used to make a backwards-compatible version I
wonder ...? I think _not_ actually, but I'm not 100% sure.
> (b) Does anyone see a simpler way to do this?
Actually passing the XML is the simplest since you send all the informations
What concerns me is to try to keep old and new versions to still communicate
okay. maybe the Preparev2/Prepare allows already the do this when falling
back if the receiving end has no Preparev2.
Yes, we will use the SupportsFeature driver call to detect if
migration V2 is supported. Xen will be changed to support both (very
simple change) and KVM will support only V2. In either case, libvirt
will have to continue to support both styles in case it needs to talk
to old libvirtd's.
> (c) Since we're adding a second version of the protocol,
does anyone
> want anything else added?
Never need a v3 ;-)
> (d) Will the domain XML alone be sufficient to recreate the exact
> qemu command line? (Seems to be the case, and in fact KVM suspend/
> restore support seems to implicitly rely on this too).
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v
5:12 p.m.
New subject: [libvirt] Re: [Libvir] KVM migration
On Mon, Apr 07, 2008 at 04:40:41PM +0100, Richard W.M. Jones wrote:
It turns out that the general migration strategy I defined[1] in
reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
sufficient to support KVM migration.
[...]
What ever happened to this? Is it being worked on somewhere by someone?
--
Soren Hansen |
Virtualisation specialist | Ubuntu Server Team
Canonical Ltd. | http://www.ubuntu.com/
5:50 a.m.
New subject: [libvirt] Re: [Libvir] KVM migration
On Fri, May 16, 2008 at 12:12:00AM +0200, Soren Hansen wrote:
On Mon, Apr 07, 2008 at 04:40:41PM +0100, Richard W.M. Jones wrote:
> It turns out that the general migration strategy I defined[1] in
> reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
> sufficient to support KVM migration.
[...]
What ever happened to this? Is it being worked on somewhere by someone?
I've been concentrating on our toolset for the Red Hat Summit next
month is what :-) Here's an updated patch.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v
4:25 a.m.
New subject: [libvirt] Re: [Libvir] KVM migration
On Mon, May 19, 2008 at 11:50:25AM +0100, Richard W.M. Jones wrote:
On Fri, May 16, 2008 at 12:12:00AM +0200, Soren Hansen wrote:
> On Mon, Apr 07, 2008 at 04:40:41PM +0100, Richard W.M. Jones wrote:
> > It turns out that the general migration strategy I defined[1] in
> > reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
> > sufficient to support KVM migration.
> [...]
>
> What ever happened to this? Is it being worked on somewhere by someone?
I've been concentrating on our toolset for the Red Hat Summit next
month is what :-) Here's an updated patch.
Hum, what is blocking pushing this update ? You're afraid of changing
the network interfaces now (IMHO the earlier the better !) ? Lack of
review ? Lack of testing ?
Daniel
--
Red Hat Virtualization group http://redhat.com/virtualization/
Daniel Veillard | virtualization library http://libvirt.org/
veillard(a)redhat.com | libxml GNOME XML XSLT toolkit http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
4:35 a.m.
New subject: [libvirt] Re: [Libvir] KVM migration
On Tue, May 20, 2008 at 05:25:35AM -0400, Daniel Veillard wrote:
On Mon, May 19, 2008 at 11:50:25AM +0100, Richard W.M. Jones wrote:
> On Fri, May 16, 2008 at 12:12:00AM +0200, Soren Hansen wrote:
> > On Mon, Apr 07, 2008 at 04:40:41PM +0100, Richard W.M. Jones wrote:
> > > It turns out that the general migration strategy I defined[1] in
> > > reference to Xen, ie. the 3 steps of Prepare/Perform/Finish, isn't
> > > sufficient to support KVM migration.
> > [...]
> >
> > What ever happened to this? Is it being worked on somewhere by someone?
>
> I've been concentrating on our toolset for the Red Hat Summit next
> month is what :-) Here's an updated patch.
Hum, what is blocking pushing this update ? You're afraid of changing
the network interfaces now (IMHO the earlier the better !) ? Lack of
review ? Lack of testing ?
Lack of testing. Apparently oVirt people are going to play with it at
some point.
Rich.
--
Richard Jones, Emerging Technologies, Red Hat http://et.redhat.com/~rjones
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into Xen guests.
http://et.redhat.com/~rjones/virt-p2v
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6 comments
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