[VoiceOps] Load balancing

Alex Balashov abalashov at evaristesys.com
Fri Nov 6 21:53:34 EST 2009

John Todd wrote:

> I, for one, would be very interested to see anyone's results with the 
> logically extreme version of "keeping state", meaning keeping media state.
> Asterisk can't perform failover between two discreet systems and 
> maintain media state, if media is indeed being handled as a B2BUA and 
> RTP relay.  We (Digium) have been asked a few times about it, but the 
> engineering effort is much much larger than the payoff and nobody from 
> the open-source community has stepped forward with any code.  The amount 
> of synchronization data that would have to be exchanged between two 
> systems running RTP and signaling is large.  VERY large.  That's not to 
> say it can't be done, but I just haven't seen it done even with VMWare 
> or other VM-based systems which may claim to be able to synchronize 
> instances between chassis platforms.
> Most failures aren't hardware or chassis-based; they're software-based, 
> so duplicating corrupted memory structures between two machines will 
> give you (surprise!) two dead machines, or two dead apps on two machines 
> regardless of the application being used.  So this has limited use.  
> Anyone who has code that relays minimal state WITHOUT mirroring the 
> whole app/system so that two instances of (for instance) Asterisk could 
> be synchronized without shared fate... I'll be very VERY interested in 
> that.  :-)
> So: has anyone out there done this with any RTP-capable systems running 
> on Linux (Asterisk or otherwise)?  If so, can you post notes and 
> operational techniques?

I believe this effort is a specious and misguided waste of time, and 
the interest in it is principally the expression of the following 
deficiencies in the thought process of those doing the asking:

(1) Exaggerated, megalomaniacal perceptions of the relative importance 
of four-9s vs. nine-9s uptime, and with it, lack of cursory 
accompanying understanding of the Pareto principle;

(2) Lack of non-superficial comprehension of how the technology works, 
which you have covered quite well with your post.

These are not satellite guidance systems.  That level of failover is 
simply unnecessary, although I have met more than one proud ITSP owner 
who is prepared to solicit proposals for magic.

Alex Balashov - Principal
Evariste Systems
Web     : http://www.evaristesys.com/
Tel     : (+1) (678) 954-0670
Direct  : (+1) (678) 954-0671

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