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I am in the process of setting up a standby server for a PostgreSQL 9.3 install. I was looking to use pg_basebackup to get the initial starting point for the standby server. However, the documentation for pg_basebackup mentions that it will "[make] sure the system is automatically put in and out of backup mode". I can't seem to find what "backup mode" is, or what effects that will have on the production server.

The documentation for pg_basebackup does mention that the backup is "taken without affecting other clients to the database", but I need to be certain that "backup mode" won't do anything unexpected to the production server.

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In and out of backup mode means that it will execute the pg_start_backup() function at the beginning and pg_stop_backup() at the end.

They're described at Backup Control Functions in the documentation.

The effect of pg_start_backup() on the production server is a possible I/O spike caused by checkpointing (applying the transaction log also named xlog or WAL files to the final data files).
This may be mitigated by the option --checkpoint=fast|spread but it's already spread by default according to pg_basebackup manpage.

"Not affecting other clients" means that SQL programs can continue all operations without restriction during the backup. Possibly with a loss in performance due to the I/O load caused by the backup itself, but there's no way to avoid that.

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Thank you so much! I did read a bit on the page for pg_start_backup() but still didn't feel very confident. –  Rodel30 Oct 8 '13 at 13:17

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