Re: [Postgres-xc-general] Postgres-XC Performance

[Mason S. <ma...@st...>]

On Fri, Aug 23, 2013 at 12:46 PM, Aurelienne Aparecida Souza Jorge <
aur...@gm...> wrote:

> Hello!
>
> I'm a post-graduation student and my conclusion work is about Postgres-XC.
> I've read a lot about the project and I really think this is a powerful
> tool. Unfortunately, I couldn't achieve the performance I had expected.
>
> I've configured a cluster with 4 virtualized servers (all of them on the
> same hardware using Virtual Box):
> Server 1: gtm
> Server 2: 1 gtm_proxy + 1 datanode + 1 coordinator
> Server 3: 1 gtm_proxy + 1 datanode + 1 coordinator
> Server 4: 1 gtm_proxy + 1 datanode + 1 coordinator
>

How many cores are on the underlying system?  Keep in mind that those
resources are going to be shared. Are you CPU bound?  Was your base
PostgreSQL instance for comparison also running in a VM?

In addition, does each server have its own dedicated storage? Or are they
all contending for the same physical device underneath?  Do you have fsync
on (and is it really fsync'ed by the VM)?


>
> The version of Postgres-XC I'm using is 1.0.3, and the OS in all servers
> is Debian 7.
>
> I used pgbench to compare the number of transactions per second in
> Postgres-XC and in a standalone PostgreSQL server. Postgres-XC achieved
> only half TPS compared to PostgreSQL. The test was basically consisted of
> inserts into distributed tables (I used a custom script in pgbench) simulating
> many clients simultaneously.
>
> I would like to know what configuration would be enough to have a better
> performance than PostgreSQL.
>
> - How many servers would be enough to have a write/read scalability
> compared to a single PostgreSQL?
>
> - Would it be a problem to have all servers on the same hardware?
>
> - Should I distribute the workload among all coordinators? I'm basically
> using one coordinator, once I couldn't find a way to use all of them simultaneously
> with pgbench.
>
> I would be very thankful if you could help me.
>
>
> Regards,
>
> Aurelienne Jorge.
>
>
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-- 
Mason Sharp

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