Re: Use of rsync for data directory copying

On Jul 9, 2012, at 7:48 PM, Bruce Momjian wrote:

> Rsync is popular with Postgres users, but I don't understand how they
> are using the default check mode (file size, modification time) to
> synchronize shut-down data directories?  It seems they would have to use
> --checksum because it is too easy for files to change in the same
> second, and for a backend to write into the middle of a file.
>
> Is everyone who is using rsync with Postgres also using --checksum mode?


I must be missing something, if they're shut down you can't write to them. =)

I do use rsync though for resyncing my mirror's, it's been working great so far. I assume
that the WAL fixes anything that gets goofed up in the copy. (hopefully I've been assuming correctly.)


---
#!/bin/ksh

SOURCE=masterdbserver

. /etc/sysconfig/pgsql/postgresql-9.1

export PGDATA
export PGPORT

rm -f $PGDATA/failover

pg_ctl stop -D $PGDATA -m immediate
psql -h $SOURCE -p $PGPORT <<EOD
checkpoint;
select pg_start_backup('mirror');
EOD
rsync -avv --delete-delay \ --exclude postgresql.conf  \ --exclude pg_hba.conf \ --exclude server.conf \ --exclude
archive.conf\ --exclude recovery.conf \ --exclude recovery.done \ --exclude pg_ident.conf \ --exclude failover \
--excludepg_xlog \        --exclude postmaster.pid \  $SOURCE:$PGDATA/ $PGDATA 
psql -h $SOURCE -p $PGPORT -c "select pg_stop_backup()"
cp $PGDATA/recovery.done $PGDATA/recovery.conf
pg_ctl start -D $PGDATA