Re: [Postgres-xc-general] ERROR: Failed to get pooled connections

[Vladimir S. <vst...@gm...>]

On Tue, Jul 31, 2012 at 8:02 PM, Mason Sharp <ma...@st...> wrote:

> I think you misunderstood. Tables can be either distributed or
> replicated across the database segments. Each segment in turn can be
> have multiple synchronous replicas, similar to PostgreSQL's
> synchronous replication.

Thank You very much for clarification! It is the same as written on XC
home page. If I don't understand that, I couldn't write all above in
this thread as well I couldn't provide overall tests of all of those
feature before write here. Do You read this thread completely?

> multiple nodes, gaining write scalability.  The overhead and added
> latency for having replicas of each database segment is relatively
> small, so you need not think of that as preventing "write balance", as
> you say.

Write scalability ( I prefer term, which You are using here - "write
balance" because scalability means changing of data nodes number)
means that You can write to all N nodes faster then to single one.
This is possible only for distributed data. If You write all 100% data
to every node it is not possible. If You don't want consider standby
server as node - it is wrong, because for load balancing every
hardware node is meaningful.

Meanwhile, I don't like idea of using standby at all, because it
should be consider as external solution. When I wrote above about
"asynchronous replication", I imply improving existing XC replication
technology, but on node level instead of table.

> know about database segment replicas. Up until now the project has
> focused on the challenges of the core database and not so much dealing
> with stuff on the outside of it, like HA.

I thought HA & LB is main feature of any cluster.