PostgreSQL disk fragmentation causes performance problems on Windows

I am using PostgreSQL to log data in my application. A number of rows are added periodically, but there are no updates or deletes. There are several applications that log to different databases.

This causes terrible disk fragmentation which again causes performance degradation when retrieving data from the databases. The table files are getting more than 50000 fragments over time (max table size about 1 GB).

The problem seems to be that PostgreSQL grows the database with only the room it need for the new data each time it is added. Because several applications are adding data to different databases, the additions are never contiguous.

I think that preallocating lumps of a given, configurable size, say 4 MB, for the tables would remove this problem. The max number of fragments on a 1 GB file would then be 250, which is no problem. Is this possible to configure in PostgreSQL? If not, how difficult is it to implement in the database?

Thank you,
JG