Re: [Xen-devel] driver domain crash and reconnect handling

[Zoltan Kiss <zoltan.kiss@xxxxxxxxxx>]

On 24/01/13 14:06, George Shuklin wrote:
> 24.01.2013 17:25, Paul Durrant ÐÐÑÐÑ:
> > > Some notes about guest suspend during IO.
> > >
> > > I tested that way for storage reboot (pause all domains, reboot ISCSI storage
> > > and resume every domain). If pause is short (less that 2 minutes), guest can
> > > survive. If pause is longer than 2 minutes, guests in state of waiting for io
> > > completion, detects IO timeout after resuming  and cause IO error on virtual
> > > block devices. (PV).
> > To be clear here: do you mean you *paused* and then unpaused the VMs, or 
> > *suspended* and then resumed the VMs? I suspect you mean the former.
> >
> >     Paul
> Pause, of cause. My bad.
If you would do a suspend, the frontend driver flush out disk IO 
operations before suspend reached, and therefore there won't be anything 
to timeout after resume. However, if the storage driver domain just 
crashed, I guess the guest would crash at suspend. Maybe we can try out 
something to save the the ring buffer, and replay them back once the 
backend come back (but before resuming the guest). But I'm not sure 
whether the guest would handle the timeouts after the resume first, or 
cancel them if the requests were succesfully responded.
Zoli

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