Hi all, I'm running Postgres 9.6 and backing it up once a while simply by stopping the cluster and using rsync on file level. One day I've recognized that some files for tables in my backup and prod system have the same size and last written timestamp, while the data itself actually differs. I recognized that using rsync with checksums and wondered why much more data gets transferred than expected. So I calculated hash sums for those files and those were different. The important thing is that after rsync with checksums transmitted those changed files with unmodified timestamps, the hash sums of the files were back in sync again. So it seems very unlikely that the problem is during rsync copying data itself. I can only think of two reasons: Either Postgres has some behaviour where data is actually written to files without changing timestamps or my backed up data gets modified somehow, which sounds like corruption, because as a backup, it shouldn't get modified of course. So, is there any such functionality in Postgres, writing data without changes to timestamps of the file in the file system? Any other ideas on where those hash differences could come from? Sounds like to be sure I need to regularly generate hashes of my backups and compare those to unmodified files in the backup source. The backups are not stored on checksumming file systems like BTRFS or ZFS, so silent data corruption might be an aspect. Thanks for your ideas! P.S.: Posted that on SU as well, but didn't get much attention. https://superuser.com/questions/1216259/does-postgres-ever-write-to-tables-without-file-system-timestamps-getting-update Mit freundlichen Grüßen, Thorsten Schöning -- Thorsten Schöning E-Mail: Thorsten.Schoening@xxxxxxxxxx AM-SoFT IT-Systeme http://www.AM-SoFT.de/ Telefon...........05151- 9468- 55 Fax...............05151- 9468- 88 Mobil..............0178-8 9468- 04 AM-SoFT GmbH IT-Systeme, Brandenburger Str. 7c, 31789 Hameln AG Hannover HRB 207 694 - Geschäftsführer: Andreas Muchow -- Sent via pgsql-admin mailing list (pgsql-admin@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-admin
