After @daftaupe convinced me to give #btrfs a try, I just learned how to mount multiple #subvolume|s of a #LUKS #encrypted devices through #pam_mount:
@daftaupe @martin
Seems that things change, but according to the FAQ, there are still some issues with this matter (know how much Space left and use it)
https://btrfs.wiki.kernel.org/index.php/FAQ#Why_is_free_space_so_complicated.3F
Il still think that mixing réplication (raid) and file system is a very bad idea.
@martin @hoper There's nothing magical :) it's basically having 2 btrfs partitionned drives, making a snapshot of a subvolume and sending that read-only snapshot from one to the other disk. That prevent us from the use a of a tool like rsync as there's an option to send only the increment when you already have subvolumes on the other drive. Based on : https://btrfs.wiki.kernel.org/index.php/Incremental_Backup
@martin
In m'y mind, a snapshot is not a clone. It's just a sort of "diff" of two devices. Something that you can't separate from it's source.
So I dont understand how you can have a filesystem somewhere, and a snapshot of it elsewhere that can be usefull. A copy, yes. Easy. But a snapshot ? Guess there is plenty of things I dont understand about btrfs.
Maybe the first reason for me to not like it :o)
@hoper @martin I did mention another disk or drive, it's up to you to think that it's in the same server.