Re: [Devel] Re: swsusp done by migration (was Re: [RFC][PATCH 1/5] Virtualization/containers: startup)

[Sam Vilain <sam@vilain.net>]

Vasily Averin wrote:
>>When checkpointing it is important to preserve all state.  If you are
>>doing transparent highly available computing, you need to make sure all
>>system calls get the same answers in the clones.  So you would need to
>>virtualise the entropy pool.
> From my point of view it is important to preserve only all the determinated state.
> Ok, lets we've checkpointed and saved current entropy pool. But we have not any
> guarantee that pool will be in the same state at the moment of first access to
> it after wakeuping. Because a new entropy can change it unpredictable.
> Am I right?

Good point.

In general this comes under the heading of "when doing highly available
computing, ensure each of your computing replicas get exactly the same
inputs and always double-check their outputs".

There are lots of 'inputs' that affect the state of the system; when I
referred to "/dev/random and the system clock", I was figuratively
referring to these.  Others might include timing of disk IO events, for
instance.

I'd rather not discuss this too much; it was intended to be a flippant
"wishful thinking" thought, and is certainly not something I have spent
the necessary time investigating to discuss well :).

Sam.