Re: Virtualization vs. sharing a server

On Mon, Mar 29, 2010 at 4:50 PM, Ramiro Barreca <rbarreca(at)gmail(dot)com> wrote:

> As this is a very heterogeneous platform (from Oracle 10g, SQL Server 2008,
> Firebird 2.1, Mysql 5, Postgre 8.4 up to Informix 5 and even COBOL apps) whe
> are evaluating Virtualization or just sharing a server among PostgreSQL and
> firebird or MySQL.
> As Virtualiaztion is almost discarded after reading many articles that
> locate this option in the "don'ts-list", we want to know your experience (if
> any) about installing a PostgreSQL and a Firebird server in the same Linux
> server.

Virtualisation is not a bad option per-se. Just don't expect the same
performance as if it was running on bare metal.

I have a VPS with Xen Hypervisor, 4 GB of RAM at the moment, running
PostgreSQL 8.4, MongoDB and MySQL. No problems at all. The setup
includes LVM, virtual disks are images on real disk. It's working just
fine, but it won't "hold" forever. It's a "cheap" solution at the
moment, affordable and performs very well. But I don't expect it to
perform as if there were no virtualisation layer.

> Is there a configuration option we need to consider to share this server?
> What is the recomended hardware for a PostgreSQL server that has to support
> between 500 and 1000 simultaneous user connections? Is there a whitepaper
> about this?

You definitely want to do connection pooling when possible, or try to
share tables among several database servers to spread the load. 500 up
to 1000 simultaneous connections are very resource consuming, no
matter which hardware you have. Of course it also depends on the type
of application your users are running...

--
Jaume Sabater
http://linuxsilo.net/

"Ubi sapientas ibi libertas"