> First of all, thanks so much for the reply. To be clear, as stated in my > original post, if a user is interacting with the PostgreSQL database, > changes to the data folder continue even after the PG_START_BACKUP > command has been issued. This implies to me that the contents of any > copy of the data folder may be unreliable. i.e. the copy may not reflect > the state of the data folder either before the copy started or after the > copy has finished. It may reflect the state of the data folder in some > transient form. Assuming this is true, is the copy still usable for > restoration? If so, how does PostgreSQL get the data folder to a stable > state? Is it by the use of the WAL files that may be created during the > backup process and the restore.config file? The copy is not useful by itself, but is when used in conjunction with the WAL archives. It is all explained, much better than I could do it, in http://www.postgresql.org/docs/9.0/interactive/continuous-archiving.html There are other backup strategies too. http://www.postgresql.org/docs/9.0/interactive/backup.html -- Ian. > -----Original Message----- > From: Ian Lea [mailto:ian.lea@xxxxxxxxx] > Sent: Friday, April 08, 2011 3:55 AM > To: David Roland > Cc: pgsql-admin@xxxxxxxxxxxxxx > Subject: Re: pg_start_backup - backups > >> Attempting to run a backup with the database online. I first issue >> 'PG_START_BACKUP', then copy the contents of the postgresql data >> folder, then issue 'PG_STOP_BACKUP'. The database service remains >> running during the copy. If queries continue to hit the database after > >> the PG_START_BACKUP command is issued changes to the data folder are >> possible, which can cause copy errors (for instance, a file not found >> exception). The file copy method first creates a string array of the >> data folder contents (all folders and >> files) and then processes the array, copying one file at a time. What >> am I doing wrong? > > You need to use a program to do the copying that can accept changes to > files as it runs. rsync is a common choice and has the massive > advantage that it only takes changes and is therefore, after the first > run, quick. > > See > http://www.postgresql.org/docs/9.0/static/continuous-archiving.html#BACK > UP-BASE-BACKUP > or use your favourite search engine to find more info. > > > -- > Ian. > -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
