We just did this. I did a pg_dumpall using 8.1. Then we fired up 8.2 while 8.1 was still running. Uploaded the data to 8.2. Then shut 8.1 down. This allowed us to have the database unavailable for a very short time.
Carol
Carol,
If this is truely what you did, you are a very lucky person. You are always supposed to dump the old database using the new versions pg_dump/pg_dumpall. That way, pg_dump/pg_dumpall can set up the data for any changes made by the newer version.