Re: How robust is postgresql ?

On Tue, 6 Mar 2001, Simon Crute wrote:

>   We're writing an app in Perl and currently using Oracle as the backend
> database (via the perl DBI) but due to the costs when we put this live we're
> thinking of useing Postgresql.

Good choice!  Version 7.1, now in beta and due out very soon, has a lot of
new stuff that is very smart and cool.

> However we need to know how crash resistant Posgresql is. Oracle has the
> "Archive log mode" which writes a log of everything that's casued the
> database to change. This allows you to recoved it properly in the event of a
> crash.
>
> Does Postgresql have anything simmilar ? I've read about Postgresql's "fsync
> mode". Does this guarantee that the data is written to the disk properly and
> that the in the even of a crash (such as power outage etc) the database will
> still be correct ?

7.1 has write-ahead logging (WAL), which does what you are looking for.
See http://www.postgresql.org/devel-corner/docs/admin/wal.html

The fsync mode also helps with data integiry, but it *really* slows down
the system, unfortunately.

> The other question is Backups. Is there anyway to take diferential backups ?
> I.E do a full dump periodically, and then make diferential backups from time
> to time (preferably to a differet box)

You can do a database dump and back up the SQL generated, or do a
filesystem backup.  See
http://www.postgresql.org/devel-corner/docs/admin/backup.html for
information on the specifics.

-- Brett
                http://www.chapelperilous.net/~bmccoy/
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