r/bcachefs

I switched from a btrfs setup to bcachefs mainly because I like the folder/file based redundancy for it's much better flexibility.

But with my old setup I set up my disk to go to sleep after well with hdparm this setting:

>-S 241

Which should be 30minutes so the harddisk gone to sleep when I did not read from it, now with bcachefs I think it never sleeps so I think the FS does background task all the time even I don't change anything on the setup since many days.

But when I use "fs usage" the "Leaving" column shows some numbers so I think it does something in the back? Or do I misinterpret that?

Maybe I am wrong but I think some background task from bcachefs creates accesses on the harddisk and keeps them from sleeping.

https://evilpiepirate.org/git/bcachefs-tools.git/tree/Changelog.mdwn

All kinds of stuff; we're looking pretty good on stability and now it's mostly people just people turning up all kinds of interesting corner cases.

Lots of FUSE patches too - we now have fuse + xfstests running through the CI. The goal there is if there's another Arch hiccup or anything like that, fuse should be a solid and stable (just slow) fallback.

I was thinking about this today, large ZFS arrays can have multiple vdevs each one with RAIDZ2, so you could lose 2 drives on each vdev without losing the array or the data.

But bcachefs, even with failure domains, stores the metadata using 2 or 3 replicas, so no matter the arrangement, losing 2 or 3 disks would lose the entire array.

Also, it seems that using failure domains and replicas=2 could emulate a RAID10, but that is not guaranteed (just preferred, according to the PoO), and in my tests storing 600MB in a 4 devices (2+2) left ~40MB in the same domain with 4 equally-sized loop devices.

Is this correct, or am I missing something?