Re: Multiple Postmasters on Beowulf cluster

Aside from the problems associated with making multiple Postgresql
processes access a single data store, wouldn't you be dealing with a
severe performance penalty? Since disk is typically the slowest part of
any system, I would imagine that 45 nodes, all beating on one network
file system (or a multiport filesystem for that matter) would tend to
slow things down dramatically. I would think that it would be better to
make 45 separate copies of the database and then if there are updates,
make some kind of process to pass all of the transactions to each
instantiation of the DB. Granted, the disk space would increase to 45X
the original estimate. How much updating/changing goes on in the Db?

Cheers!

Bob

On Sat, 2002-07-27 at 11:24, Jan Hartmann wrote:
> Hello,
>
> I am using Postgresql with PostGis and the Minnesota MapServer on a Beowulf
> cluster for web-mapping applications. It runs fine on one node, producing
> very fast interactive maps for an Apache/PHP web server. However, the
> cluster consists of 45 nodes, all using a shared user file system. Is it
> possible to start up a postmaster on every node, using the same database?
> The backend processes themselves would be completely autonomous, but they
> would have to share their data from the same source. To simplify things,
> only read-access is necessary. Would this be possible, and if so, how can
> the different postmasters be made to use a different postmaster.pid file
> (which is located in the shared data directory)?
>
> It would be an interesting way for using the cluster, as the individual map
> layers can be independently constructed on different nodes, and only finally
> have to be put together in a complete map. Essentially, MapServer constructs
> a map from layers, where each layer originates from an individual PostgreSQL
> connection, even when using only one database. In a cluster solution
> therefore, no communication between the nodes would be required. Even the
> data could be distributed over the nodes and put into different databases,
> but this would inevitably lead to much duplication and a set of databases
> that would be very difficult to administer. In the archives, I saw some
> mention of work in progress on distributed databases, but for this I don't
> need much in the way of distributed facilities, just reading shared data.
>
> Any help would be very much appreciated. It certainly would be a great
> example of PostgrSQL's advanced geometrical capabilities!
>
>
> Jan Hartmann
> Department of Geography
> University of Amsterdam
> jhart(at)frw(dot)uva(dot)nl
--
Robert M. Meyer
Sr. Network Administrator
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