Linux OpenSUSE with btrfs: Supported?

[DaltonST]

Should Calibre work 'properly' using Linux OpenSUSE with btrfs?

[kovidgoyal]

Originally Posted by DaltonST

Should Calibre work 'properly' using Linux OpenSUSE with btrfs?

As far as I know it should. Cant say I have tested it personally though

[isarl]

I'm not sure about OpenSUSE or anything it might do differently, but if it helps at all, I run Calibre with zero issues on Arch Linux using multiple btrfs filesystems. My root partition is btrfs, and so is my home partition – Calibre is installed to the root partition (through my package manager) and my Calibre Library is stored in my home partition.

If you start doing strange things like restoring a snapshot while Calibre is open and running, then I could easily imagine strangeness, in exactly the same way that I would expect strangeness if Calibre was running and I went and started messing about with files in the library directory. But as long as you're restoring a proper snapshot of the entire Calibre library directory, and Calibre is not open at the time, then I can't see how btrfs could otherwise cause problems.

[DaltonST]

A Calibre user of one of my plugins has been having an impossible time getting APSW to connect (ATTACH) to multiple Libraries sequentially. She uses OpenSUSE with btrfs, and has had no problems with Calibre until now with this very specific issue. APSW is spectacularly unhelpful as to why it gets an OpenError; debugging log shown nothing worthwhile.

The connection for attachment is supposed to look like this, but always throws an exception, OpenError, just after the "Attaching to New Source Library:" message, where the APSW SQL "ATTACH DATABASE 's:/calibre/calibrelibrarycodes/metadata.db' AS 'SOURCE' ;" is executed by APSW.

ATTACH DATABASE 's:/calibre/calibrelibrarycodes/metadata.db'  AS 'SOURCE' ;
length of path:  42
Attaching to New Source Library: s:/calibre/calibrelibrarycodes/metadata.db
Now Attached to New Source Library: s:/calibre/calibrelibrarycodes/metadata.db
PRAGMA SOURCE.busy_timeout = 4000;
Finished: apsw_attach_to_source

So far, the closest random, odd issue might be found in: https://btrfs.wiki.kernel.org/index.php/Gotchas regarding the Fragmentation of application databases. She is going to defrag her btrfs system and report back the results.

I don't use Linux except for my Raspberry Pi Manjaro/Arch Calibre server.

DaltonST

[kovidgoyal]

What's with the s:/ prefix on those paths?

[DaltonST]

That was the example debug log from my testing to ensure it still works on my Windows 11 system, not the OpenSUSE btrfs path of the user's latest log that I just got: */home/susan/calibre/testlibrary

She defragged btrfs, and nothing changed.

[nixR3ad]

If this comes up again, ask the user if they disabled copy-on-write for their database. There is really bad advice out there about btrfs and databases. Users commonly (and incorrectly) do

chattr +C /path/to/database

This is practically the mantra. But this disables CoW (and all the data integrity features btrfs employs). The damage is silent until a triggering event like replication, balance, or defrag.

I have been using Calibre on a multi-disk btrfs system for years, and the only problems have been self-made. Aside from the time I believed it would be wise to convert my Kobo's filesystem to btrfs, the worst experiences came from disabling CoW for things like databases and VMs.