[libvirt] disk XML for error policy

[Dave Allan]

On 03/17/2010 11:09 AM, Daniel P. Berrange wrote:
> On Tue, Mar 16, 2010 at 10:14:26PM -0400, Dave Allan wrote:
>> Hi Dan,
>>
>> What do you think of this for the disk XML specifying what to do on error:
>>
>>      <disk type='file' device='disk'>
>>        <source file='/storage/guest_disks/libgdu'/>
>>        <target dev='vda' bus='virtio'/>
>>        <on_err rerror='stop' werror='stop'/>
>>      </disk>
>
> I'm in two minds as to whether we really need separate policies for read
> and write. I know QEMU supports that, but even those who implememted it
> told me it was rather redundant&  a historical accident because they did
> not want to rename the existing 'werror' attribute when they added the
> 'rerror' bit. So unless someone has a compelling reason for them to be
> separate I think we can have a single policy.

Heh, makes sense to me; one policy it is.

> If we follow the style of the<on_reboot>  <on_poweroff>  elements we'd
> have something like
>
>    <on_error>stop</on_error>
>
> My only other thought would be to do it as an attribute on the existing
> <driver>  element in disks, where we have disk format&  cache mode already

Adding an attribute seems like a nice way to do it.

Dave