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

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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