From 70f173caa7b4628978e9d1164bb628233e51b10d Mon Sep 17 00:00:00 2001 From: Helmut Grohne Date: Mon, 23 Sep 2024 09:52:14 +0200 Subject: [PATCH] FAQ: Why is backing up an unmodified FAT filesystem slow on Linux? --- docs/faq.rst | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/docs/faq.rst b/docs/faq.rst index e3de4bf95d..f8d830660b 100644 --- a/docs/faq.rst +++ b/docs/faq.rst @@ -357,6 +357,17 @@ to change them. Use ``borg repo-compress`` to efficiently recompress a complete repository. +Why is backing up an unmodified FAT filesystem slow on Linux? +------------------------------------------------------------- + +By default, the files cache used by BorgBackup considers the inode of files. +When an inode number changes compared to the last backup, it hashes the file +again. The ``vfat`` kernel driver does not produce stable inode numbers by +default. One way to achieve stable inode numbering is mounting the filesystem +using ``nfs=nostale_ro``. Doing so implies mounting the filesystem read-only. +Another option is to not consider inode numbers in the files cache by passing +``--files-cache=ctime,size``. + Security ########