I recently came across a presentation given on migrating a very large database (as in, tables with 1.8 billion rows) from Oracle to PostgreSQL. It describes some of the issues they had along the way, including having to move from Linux to OpenSolaris due to stability issues.
One of the more interesting challenges they had to solve was the lack of support for partitioning in PostgreSQL. Oracle allows you to partition tables, so for example if you had a large table, you can cluster the data into various segments - dates in their case. The reason for doing this is to allow you to put less frequently accessed data on cheaper storage (say, SATA instead of SCSI).
The solution in this case was to use PostgreSQL’s support for table inheritance (implementation details in the presentation). This allowed them to easily add and delete new partitions. Database archiving is always a hassle, and it also seems like this might make that easier as well.
I’ve never used inheritence in PostgreSQL, so I don’t know what kind of overhead it adds, but no performance issues were noted in the presentation. Regardless, this seems like a very interesting solution to a pretty common problem.