Thank you for the complementary explanation! The computer uses an SSD so I'm not concerned about fragmentation indeed.
Fred Kite Le 5 août 2025 16:35:07 GMT+02:00, Andy Smith <[email protected]> a écrit : >Hi, > >On Tue, Aug 05, 2025 at 08:49:43AM +0200, [email protected] wrote: >> Would it be safe to perform the deduplication with a single command on >> /home instead of each user's folder separately? Will it create >> problems if the same file is found in several home folders but has >> different ownership and permissions? > >It can leak information about what is shared, but this is perhaps not of >concern in your case. > >For example, if user "foo" has a large file and runs "filefrag -e" on it >then they can see the filesystem extents that compose the file. Your >system later deduplicates this file by making one or more of its extents >point to the same extent(s) within the storage of user "bar". User "foo" >can now run "filefrag -e" again and see that some extents have changed. >They now know that this data *also* exists somewhere else on the >filesystem. They don't know where, but this is not information that they >had before. > >Secondly, and this is not related to cross-user deduplication but more a >question of the amount of deduplication: on HDD media frequent >deduplication can fragment files into lots of pointers to duplicate >extents, reducing streaming file read performance as a sequential read >has to move the read about across the disk. Obviously not much of a >factor for non-rotational media. > >That's all that comes to mind. > >Thanks, >Andy > >-- >https://bitfolk.com/ -- No-nonsense VPS hosting >
