Hi, Juan,
Juan Casero (FL FLC) wrote:
> Ok that is beginning to become clear to me. Now I need to determine if
> this server is worth the investment for us. Maybe it is not a speed
> daemon but to be honest the licensing costs of an SMP aware RDBMS is
> outside our budget. When postgresql starts does it start up a super
> server process and then forks copies of itself to handle incoming
> requests?
It starts a super server process (Postmaster) and some background
processes (background writer, stats collector). For each incoming
connection, the postmaster forks a single-threaded backend process,
which handles all queries and transactions on this connection, and
terminates when the connection terminates.
So as a thumb-rule, each connection can utilize only a single CPU. You
can utilize a few more CPUs than you have simultaneous connections, due
to the background processes and the OS needing CPU for I/O, but thats
rather marginal.
AFAIK, Bizgres MPP has extended the backend processes to be multi
threaded, so a single connection can utilize several CPUs for some types
of queries (large data sets, sorting/joining/hashing etc.). Btw, I
presume that they might offer you a free test license, and I also
presume their license fee is much lower than Oracle or DB/2.
> Or do I have to specify how many server processes should be
> started up?
You can limit the number of server processes by setting the maximum
connection limit.
> I figured maybe I can take advantage of the multiple cpu's
> on this system by starting up enough postgres server processes to handle
> large numbers of incoming connections. I have this server available for
> sixty days so I may as well explore the performance of postgresql on it.
Yes, you can take advantage if you have multiple clients (e. G. a wep
app, that's what the T2000 / Niagara were made for). You have a Tomcat
or Jboss sitting on it, each http connection forks its own thread. Each
customer has its own CPU :-)
Then use a connection pool to PostgreSQL, and you're fine. The more
customers, the more CPUs are utilized.
But beware, if you have floating point maths, it will be very slow. All
8 CPUs / 32 Threads share a single FPU. So if you need floating point
(e. G. Mapserver, PostGIS geoprocessing, Java2D chart drawing or
something), T2000 is not the right thing for you.
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
Fight against software patents in EU! www.ffii.org www.nosoftwarepatents.org