Re: wal copies for high availability

> Hi,
>
> Our IT budget is not so much and even so I´m trying to set up a
> Postgresql high availability solution for our business.
>
> My managers gave me the following statements that I must follow:
> . the system could be out of service no more than 2 hours
> . last 5 minutes of work could be lost
>
> The first choice was to use slony-i and a master/slave
> configuration, but I could not use it because we have many tables
> without primary keys and the software house will charge us a lot to
> make this kind of modification.

I believe you can get slony to transparently add in a primary key for
each of those tables. This is probably your best option.

> Another cheap alternative is diarly (00:00) stop the master
> database and make a copy of the $PGDATA directory to the slave and
> during the day make regularly (5 x 5 minutes) copies of the current
> wal file to the slave too.

Check out the instructions for incremental backup. It's not
necessary to stop the database. This should work fine but you will
need to make sure you are copying the latest WAL file at least every
5 minutes.

> To recover the system we need only to apply all the logs created
> during the day to the slave and sta rt it up.

Again, see the directions for incremental backup.

http://www.postgresql.org/docs/8.1/interactive/backup-online.html

Rick