Re: Dump size bigger than pgdata size?

It might happen because of the type of data you have ( binary images).
The compression for binary files is notorious horrible since there is a
small chance of occurrence of same chars

In other words it is possible since during compression there are
additional chars added for checksums and redundancy

This would normally happen on small binary files, though.

-----Original Message-----
From: pgsql-admin-owner(at)postgresql(dot)org
[mailto:pgsql-admin-owner(at)postgresql(dot)org] On Behalf Of Nicola Mauri
Sent: Wednesday, June 21, 2006 10:30 AM
To: pgsql-admin(at)postgresql(dot)org
Subject: [ADMIN] Dump size bigger than pgdata size?

[sorry if this was previously asked: list searches seem to be down]

I'm using pg_dump to take a full backup of my database using a
compressed format:
$ pg_dump -Fc my_db > /backup/my_db.dmp

It produces a 6 GB file whereas the pgdata uses only 5 GB of disk space:

$ ls -l /backup
-rw-r--r-- 6592715242 my_db.dmp
$ du -b /data
5372269196 /data

How could it be?
As far as I know, dumps should be smaller than filesystem datafile since
they do not store indexes, etc.

Database contains about one-hundred-thousands binary images, some of
which may be already compressed. So i tried the --compress=0 option but
this produces a dump that does not fit on my disk (more than 11 GB).
I'm using postgres 8.1.2 on RHEL4.

So, what can I do to diagnose the problem?
Thanks in advance,

Nicola