[libvirt-users] Fwd: kvm

[Stefan Hajnoczi]

On Mon, Apr 22, 2013 at 10:59:25AM +0100, Gary Lloyd wrote:
> I was wondering if anyone could help me with an issue with KVM and ISCSI.
> 
> If we restart a controller on our EqualLogic SAN or there are any
> network interruptions on the storage network, KVM guests throw a
> wobbler and their files systems go into read only(centos 5.9 guest
> with virtio driver).
> 
> I have read a few forums that indicate you can set disk timeout values
> on the guests themselves but this is not possible using the virtio
> driver, which is what we are currently using.
> 
> Is there any way we can instruct KVM to pause the vm's if there is a
> storage failure and resume them when the storage comes back online ?
> 
> We are currently running Centos 6.4. There seems to be a werror='stop'
> and rerror='stop' options to achieve this but if I try to put these in
> options in the libvirt xml file for a vm, libvirt appears to be
> removing them.

Please email libvirt-users at redhat.com for questions about libvirt in the
future.

This is a question about libvirt domain XML.  The documentation is here:
http://libvirt.org/formatdomain.html#elementsDisks

The attribute is called "error_policy".  The documentation says:

  The optional error_policy attribute controls how the hypervisor will
  behave on a disk read or write error, possible values are "stop",
  "report", "ignore", and "enospace".Since 0.8.0, "report" since 0.9.7 The
  default setting of error_policy is "report". There is also an optional
  rerror_policy that controls behavior for read errors only. Since 0.9.7.
  If no rerror_policy is given, error_policy is used for both read and
  write errors. If rerror_policy is given, it overrides the error_policy
  for read errors. Also note that "enospace" is not a valid policy for
  read errors, so if error_policy is set to "enospace" and no
  rerror_policy is given, the read error policy will be left at its
  default, which is "report".

Stefan