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From Eric Evans <>
Subject Re: Facebook messaging and choice of HBase over Cassandra - what can we learn?
Date Sun, 21 Nov 2010 17:56:56 GMT
On Sun, 2010-11-21 at 11:32 -0500, Simon Reavely wrote:
> As a cassandra user I think the key sentence for this community is:
> "We found Cassandra's eventual consistency model to be a difficult
> pattern to reconcile for our new Messages infrastructure."

In my experience, "we needed strong consistency", in conversations like
these amounts to hand waving.  It's the fastest way to shut down that
part of the discussion without having said anything at all.

> I think it would be useful to find out more about this statement from
> Kannan and the facebook team. Does anyone have any contacts in the
> Facebook team?

Good luck.  Facebook is notoriously tight-lipped about such things.

> My goal here is to understand usage patterns and whether or not the
> Cassandra community can learn from this decision; maybe even
> understand whether the Cassandra roadmap should be influenced by this
> decision to address a target user base. Of course we might also
> conclude that its just "not a Cassandra use-case"! 

Understanding is a laudable goal, just try to avoid drawing conclusions
(and call out others who are).

This is usually the point where a frenzy kicks in and folks assume that
the Smart Guys at Facebook know something they don't, something that
would invalidate their decision if they'd only known.

I seriously doubt they've uncovered some Truth that would fundamentally
alter the reasoning behind *my* decision to use Cassandra, and so I plan
to continue as I always have.  Following relevant research and
development, collecting experience (my own and others), and applying it
to the problems I face.

Eric Evans

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