Checkpointing

[Chris Vaughan]

Hi,

Is there any way you can save a xen domain without suspending it or stopping
it?  I want to set up something so if my xen session crashes I can fire up
another xen session from the save file that I created 5 minutes before the
crash and hopefully minimize downtime.

Thanks

-- 
------------------------------
Christopher Vaughan

[Xen-users] Checkpointing

[Daniel Veillard]

On Thu, Jun 29, 2006 at 04:56:21PM -0600, Chris Vaughan wrote:
>  Hi,
>  
>  Is there any way you can save a xen domain without suspending it or stopping
>  it?  I want to set up something so if my xen session crashes I can fire up
>  another xen session from the save file that I created 5 minutes before the
>  crash and hopefully minimize downtime. 
  Doesn't work in general because you would have to save the state of the
filesystems too. Xen operations don't allow a save and continue for that
reason I was told.

Daniel

-- 
Daniel Veillard      | Red Hat http://redhat.com/
veillard(a)redhat.com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/

[Xen-users] Checkpointing

[Chris Vaughan]

So what's the difference between a "Live Migration" & "Save"
then?  Does the
live migration keep the image open and the save does not?  To me they seam
to be 2 peas in a pod but I guess I'm mistaken.

Thanks


On 6/29/06, Daniel Veillard <veillard(a)redhat.com&gt; wrote:
>  On Thu, Jun 29, 2006 at 04:56:21PM -0600, Chris Vaughan wrote:
>  > Hi,
>  >
>  > Is there any way you can save a xen domain without suspending it or
>  stopping
>  > it?  I want to set up something so if my xen session crashes I can fire
>  up
>  > another xen session from the save file that I created 5 minutes before
>  the
>  > crash and hopefully minimize downtime.
>
>    Doesn't work in general because you would have to save the state of the
>  filesystems too. Xen operations don't allow a save and continue for that
>  reason I was told.
>
>  Daniel
>
>  --
>  Daniel Veillard      | Red Hat http://redhat.com/
>  veillard(a)redhat.com  | libxml GNOME XML XSLT toolkit  http://xmlsoft.org/
>  http://veillard.com/ | Rpmfind RPM search engine http://rpmfind.net/
>  


-- 
------------------------------
Christopher Vaughan

[Xen-users] Checkpointing

[Christopher G. Stach II]

Chris Vaughan wrote:
>  So what's the difference between a "Live Migration"
> & "Save" then?  Does
>  the live migration keep the image open and the save does not?  To me
>  they seam to be 2 peas in a pod but I guess I'm mistaken.
>  
>  Thanks
>  
>   
Migration saves VM state and assumes that the filesystem does not
change.  Checkpointing would have to restore the filesystem to the same
point in time that the snapshot was taken of the VM.  Perhaps you could
swing it with CoW or something, but it doesn't work now.

-- 
Christopher G. Stach II

[Xen-users] Checkpointing

[Tracy Reed]

Christopher G. Stach II wrote:
>  Migration saves VM state and assumes that the filesystem does not
>  change.  Checkpointing would have to restore the filesystem to the same
>  point in time that the snapshot was taken of the VM.  Perhaps you could
>  swing it with CoW or something, but it doesn't work now. 
So take an LVM snapshot of the filesystem also. Maintaining network
state would seem to be the harder thing to me.

-- 
Tracy R Reed
http://ultraviolet.org

[Xen-users] Checkpointing

[Christopher G. Stach II]

Tracy R Reed wrote:
>  Christopher G. Stach II wrote:
> > Migration saves VM state and assumes that the filesystem does not
> > change.  Checkpointing would have to restore the filesystem to the same
> > point in time that the snapshot was taken of the VM.  Perhaps you could
> > swing it with CoW or something, but it doesn't work now.
>  
>  So take an LVM snapshot of the filesystem also. Maintaining network
>  state would seem to be the harder thing to me.
>   
There was talk of weaving Cruz into Xen:

http://www.hpl.hp.com/techreports/2005/HPL-2005-66.pdf

-- 
Christopher G. Stach II

[Axel Thimm]

On Thu, Jun 29, 2006 at 05:14:11PM -0600, Chris Vaughan wrote:
>  So what's the difference between a "Live Migration"
> & "Save" then?  Does the
>  live migration keep the image open and the save does not?  To me they seam
>  to be 2 peas in a pod but I guess I'm mistaken. 
Live migration ensures that the filesystem is passed as is from one
state to the other. Restoring a checkpointed system would mean that
the system would suddenly warp back in time wrt to the filesystem, or
what is effectively the same from the system's POV the filesystem
suddenly warped ahead in time.

For example: Perhaps your crash between the checkpointing and the
resuming was caused by rm -fr / and no checkpointing could undo that :)

So checkpointing in xen would only work hand in hand with block device
snapshoting.

>  Thanks
>  
>  
>  On 6/29/06, Daniel Veillard <veillard(a)redhat.com&gt; wrote:
>  >
>  >On Thu, Jun 29, 2006 at 04:56:21PM -0600, Chris Vaughan wrote:
>  >> Hi,
>  >>
>  >> Is there any way you can save a xen domain without suspending it or
>  >stopping
>  >> it?  I want to set up something so if my xen session crashes I can fire
>  >up
>  >> another xen session from the save file that I created 5 minutes before
>  >the
>  >> crash and hopefully minimize downtime.
>  >
>  >  Doesn't work in general because you would have to save the state of the
>  >filesystems too. Xen operations don't allow a save and continue for that
>  >reason I was told.
>  >
>  >Daniel
>  >
>  
>  
>   


-- 
Axel.Thimm at ATrpms.net