Re: Horizontal scalability/sharding

On Tue, Sep 1, 2015 at 3:19 PM, Josh Berkus <josh(at)agliodbs(dot)com> wrote:
> Mind you, I see a strong place for binary replication and BDR for
> multi-region redundancy; you really don't want that to be part of the
> sharding system if you're aiming for write scalability.

I mostly agree, but keep in mind that you don't have to replicate
everything. A lot of people might find it useful to replicate the
data that is common to all nodes even if they don't replicate the
sharded data.

Admittedly, there are some problems with snapshots here: if you don't
do anything special about snapshots, then what you have here will be
"eventually consistent" behavior. But that might be suitable for some
environments, such as very loosely coupled system where not all nodes
are connected all the time. And, for those environments where you do
need consistent snapshots, we can imagine ways to get that behavior,
like having the GTM consider the transaction uncommitted until it's
been logically replicated to every node.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company