[Postgres-xc-general] Node redundancy

[Josh B. <jo...@ag...>]

All:

So, in addition to the stability issues raised at the PostgresXC summit,
I need to raise something which is a deficiency of both XC and XL and
should be (in my opinion) our #2 priority after stability. And that's
node/shard redundancy.

Right now, if single node fails, the cluster is frozen for writes ...
and fails some reads ... until the node is replaced by the user from a
replica.  It's also not clear that we *can* actually replace a node from
a replica because the replica will be async rep, and thus not at exactly
the same GXID as the rest of the cluster.  This makes XC a
low-availability solution.

The answer for this is to do the same thing which every other clustering
system has done: write each shard to multiple locations.  Default would
be two.  If each shard is present on two different nodes, then losing a
node is just a performance problem, not a downtime event.

Thoughts?

-- 
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com