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? -----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
