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xen-users
RE: [Xen-users] "xm save" hanging when saving domain in "pause" state
Thanks
for your reply Michael. These are bad news... I am actually looking at options
to do offline migration, that is, take snapshots of the VMs state and their
corresponding filesystems in order to be able to fire them up in a
different host if for some reason the original host they are assigned to
crashes at some point. I have found some threads with *very* similar questions
in some mailing lists, unfortunately they don't extend to more than two
entries and have more questions than answers.
Ok.
Parameter of design? As far as I understand by "pausing" a domain, XEN is
basically indicating the scheduler not to give any other slice
to that particular VM from that point in time (until the VM is unpaused)
Why can't XEN0 just surpass the scheduler, indicate to the VM that it must
disconnect its devices (basically doing an enhanced version of "xm unpause")
and put itself in quiescent state, and wait to be notified by the VM (step 2
in your email)?. What is wrong with such approach? Am I missing
something? Would not this enable a clean checkpointing procedure?
Thanks
cc
cc, I think you could do exactly what you want with JUST xm
save, it automatically "pauses" the domain. Is there any particular reason you
CAN'T do that? Why do you need to do xm pause before xm
save?
--
Mats
On 7/14/06, Michael
Vrable <mvrable@xxxxxxxxxxx> wrote:
On
Thu, Jul 13, 2006 at 10:32:47PM -0700, Claris Castillo wrote:
> Is
there any known issue on saving a domain which is in pause state?
>
Xen hangs whenever I try to save (by means of xm save command) the state
of
> a machine which has been paused (by means of xm pause command). I
have been
> looking at the log files etc but I am not able to spot the
problem. BTW, xm
> save works prefectly fine if the domain is running
or block. The problem is
> when the domain is in pause.
Yes,
this is by design. Save/restore are a cooperative process:
1.
Xend notifies the domain that it will be saved
2. The domain disconnects
from devices, places itself into a quiescent
state, and
notifies Xen
3. After receiving this notification, xend saves the
domain's CPU state
and memory to a file
Pausing a domain
will prevent any progress from being made on step 2
(for the obvious
reason--the domain can't run), so saving will hang.
--Michael
Vrable
_______________________________________________
Xen-users
mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users
--
Claris Castillo
http://www4.ncsu.edu/~ccastil
PhD.
Candidate
Computer Science
North Carolina State University
Raleigh,
NC
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