[GENERAL] Pg and compress

[Jov]

Hi all,
We are going to use pg as data warehouse,but after some test,we found that
plain text with csv format is 3 times bigger when load to pg.we use copy to
load data.we try some optimize and it reduce to 2.5 times bigger.other db
can  avarage compress  to 1/3 of the plain text.bigger data means heavy io.
So my question is how to make data compressed in pg?is some fs  such as
zfs,berfs with compression feature can work well with pg?