From 3d260603d9ec8de67a60ba6c28629fb7d64e746e Mon Sep 17 00:00:00 2001 From: Dario Pudlo Date: Tue, 19 May 2026 11:06:12 -0300 Subject: [PATCH 1/2] Add warning about archive_command reliability --- doc/src/sgml/backup.sgml | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/doc/src/sgml/backup.sgml b/doc/src/sgml/backup.sgml index 168444e..302f8c6 100644 --- a/doc/src/sgml/backup.sgml +++ b/doc/src/sgml/backup.sgml @@ -631,14 +631,23 @@ archive_command = 'test ! -f "/mnt/server/archivedir/%f" && cp "%p" "/mn archive_command = 'copy "%p" "C:\\server\\archivedir\\%f"' # Windows which will copy archivable WAL segments to the directory - /mnt/server/archivedir. (This is an example, not a - recommendation, and might not work on all platforms.) After the + /mnt/server/archivedir. After the %p and %f parameters have been replaced, the actual command executed might look like this: test ! -f /mnt/server/archivedir/00000001000000A900000065 && cp pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065 A similar command will be generated for each new file to be archived. + + IMPORTANT: The simple cp or copy commands return success as soon as the data + is written to the operating system cache. However, PostgreSQL does not + automatically force these archived files to be flushed to physical storage as + of datafiles. In the event of an unexpected system shutdown or power failure, + files confirmed as archived might be lost from the OS cache, leading to data loss + in Point-in-Time Recovery (PITR) or issues with pg_rewind. + + To ensure data persistence, the command should include a step to synchronize + the file to disk. -- 2.54.0