pg_dump and diffrent sizes

Hello pgsql-sql,

I dump db with pg_dump v.8.1.3 on database postgresql server 7.4.7.
Data directory with my db on pg 7.4.7 had 1,8GB and
file with dump had 2,7GB.
Database have blob fields.

When I restore db on pg 8.1 - data directory have only 1GB, why?

-- 
Best regards,Maciej                          mailto:piechcio@isb.com.pl