Forum OpenACS Q&A: Re: Postgres vs. Oracle for OpenACS
Well, the answer to that question really depends on the functionality that you really need for that intranet. For example, we at Greenpeace, decided to go Oracle because of interMedia, despites the nightmare that it might be, it still provided us (two years ago, when the decision was made) with full text search within the DB in multiple languages and some other features that we don't really use... Some others (features) we do use, as mentionned, interMedia, online-backups, integrates nicely with the backup services at our provider, knowlege in-house and at the provider, etc ...
Our mid-term to long-term was to slowly migrate to PG when some of the most critical functionality would start to be available. Still not the moment but if you are migrating, asking some of these questions might help :)
Just my 2 cents.
That said, I know people at redhat are deploying postgres as HA solutions (though not with replication as far as I know) and postgres seems to be gaining ground quickly.
I have been really beating on postgres to see what breaks and it has held up really well. I have been writing up the stuff I did specifically on forums tuning if you are interested.