Re: Data duplication when moving datafiles from one server to another.

On Mon, Dec 20, 2010 at 12:22 PM, Iñigo Martinez Lasala
<imartinez(at)vectorsf(dot)com> wrote:
> Good evening.
>
> Yesterday we experienced some data duplication in several database tables
> after one sysadmin decided to test in a production environment an rsync
> script in order to migrate a database from one server to another one.
> Postgresql (8.2) was running in source server and rsync script was launched
> from second one. Second one server had a one day old copy of the same
> database. Rsync script create a datafile replica in destination server.
> Our sysadmin swear he didn't launch the script in a reverse way (that is,
> from destination to source)... so my question is
> How this data duplication could happen? Due to an rsync lock in checkpoint
> segment or transaction logs? Or he has mistaken source with destination
> server?

I use this method all the time to backup big dbs from one machine to another:

(on remote machine):
/etc/init.d/postgresql stop

(on main server):
rsync -avl --delete /data/* backupserver:/data/* # takes forever
sudo /etc/init.d/postgresql stop
rsync -avl --delete /data/* backupserver:/data/* # fast, we're just catching up
sudo /etc/init.d/postgresql start

(on remote machine):
/etc/init.d/postgresql start

You can run such a script at 2 in the morning with a few minutes
downtime without having to jump through a lot of hoops.

So, can you show us what commands your sysadmin / dba actually typed?
My guess is he left out the --delete or left the backup server db up
and running at the time of the rsync. It needs to be shut down to do
this right.