[libvirt-users] Disk space exhaustion

[Eric Blake]

On 01/30/2015 04:57 AM, Fabrizio Soppelsa wrote:
> Hello,
> 
> what happens when an instance writes data with 0% available physical
> disk space, on QCOW2 images for instance, apart from destruction and
> unpredictability?
> I'm aware that monitoring is mandatory in production environments, but
> are there other known industry tricks to deal with this? Soft/hard limit
> settings, autopause/stop, or does KVM react in doing force shut down the
> VM in question?

It's possible to run your guest with I/O error reporting - if the host
runs out of space for qemu to write to the qcow2 file, then the guest is
paused and a qemu event is raised (which in turn can be transmitted as a
libvirt event); if you then give the host more storage and resize the
disk, you can resume the guest, and the guest has no idea that there was
a transient storage shortage in the host other than the fact that a lot
of wall clock time elapsed for one operation.  Look for the
'error_policy' XML setting under
http://libvirt.org/formatdomain.html#elementsDisks

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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