Re: Help on maintaining pgsql/data folder size

"Pradeepkumar, Pyatalo (IE10)" <Pradeepkumar.Pyatalo@honeywell.com> writes:
> I am using PostgreSQL 7.4.3. The problem I am facing is that the size of
> pgsql/data folder keeps increasing and at a point the it takes up all the
> disk space and it freezes the system. The pg_xlog and the pg_clog folders
> are taking up most of the disk space. In the documentation, it says that I
> have to move the pg_xlog folder to some other location and create a symbolic
> link to that path from the original path. But the problem is for our
> application, we are using a 512 MB compact flash and there is no
> harddisk...

pg_xlog shouldn't grow unreasonably big unless you've somehow turned off
checkpointing.  pg_clog shouldn't grow unreasonably big unless you've
neglected appropriate vacuuming procedures (see the manual).  So I think
this is mostly pilot error.

It might be worth your while to reduce the size of xlog segments --- if
you have three or four 8M or 4M segments instead of three or four 16M
segments, that makes a difference when you're trying to fit in 512M.
It would require some fooling with the source code to make that happen
in 7.4; you should consider moving to 8.0 where there's just one
configuration #define to adjust.

In general though I wonder whether you shouldn't have picked another
database.  PG isn't really designed for that sort of environment.
Aside from the fact that we aren't targeting a tiny disk footprint,
we expect to rewrite the WAL files again and again and again.  What's
the write-cycles lifetime spec for your flash?

            regards, tom lane