+
+ <para>
+ <function>pg_start_backup</> can take a long time to finish.
+ This is because it performs a checkpoint, and the I/O
+ required for a checkpoint will be spread out over a significant
+ period of time, by default half your inter-checkpoint interval
+ (see the configuration parameter
+ <xref linkend="guc-checkpoint-completion-target">). Usually
+ this is what you want because it minimizes the impact on query
+ processing. If you just want to start the backup as soon as
+ possible, execute a <command>CHECKPOINT</> command
+ (which performs a checkpoint as quickly as possible) and then
+ immediately execute <function>pg_start_backup</>. Then there
+ will be very little for <function>pg_start_backup</>'s checkpoint
+ to do, and it won't take long.
+ </para>