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

[George Shuklin <george.shuklin@xxxxxxxxx>]

> > I expect the outage due to the proto-suspend is dwarfed by the outage
> > caused by a backend going away for however long it takes to notice,
> > rebuild, reset the hardware, etc etc.
> Indeed, probably the backend restoration would take at least 5 
> seconds. Compared to that, the suspend-resume and the frontend device 
> reinit is much shorter.
> Probably in storage driver domains it's better to suspend the guest 
> immediately when the backend is gone, as the guest can easily crash if 
> the block device is inaccessible for a long time. In case of network 
> access, this isn't such a big problem.
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).


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