Still a really active changelog on btrfs:
https://btrfs.wiki.kernel.org/index.php/Changelog#By_version_.28linux_kernel.29

On Mon, Sep 26, 2022 at 3:12 PM Curtis Maurand via Dng <dng@???>
wrote:

> Hello all,
>
> I currently run several Beowulf VM's under KVM that have btrfs as the main
> filesystem. One, in particular, has been giving me trouble. I kept finding
> it in a state of read-only first thing in the morning. I was attributing
> that to the backup scheme that I'm using to back up the VM in such a way
> that doesn't require me to shut the machine down for half an hour to
> transfer the image by using an external snapshot, copy the image, then
> pivot back. That is working well for all of my virtual machines.
>
> Last week, the file system started failing every couple of hours with
> btrfs errors. I cringe when that happens because btrfs does not recover
> from errors very well. However, in addition to copying the entire image I
> also take regular snapshots and and have a pretty good backup chain using
> btrbk. Generally I'm impressed with the tool. It works well. Restoration
> of data works really well from that for little things. With a filesystem
> failure, restoration of the complete VM is necessary. Ok, now that wasn't
> working. It's a 100GB VM, but the image is actually 200GB. It takes about
> 1/2 hour to copy that.
>
> btrfs has, in the past, never recovered very well. I'm no sure why that
> was, but if I ever used btrfs check --repair on a file system it always
> resulted in disaster. I had to rebuild a machine from scratch once and I
> was able to restore data from the snapshots successfully, but that took
> days to complete.
>
> In my preparations for Hari Kari I decided to try to recover the partition
> using the btrfs recovery tool. I linked a chimaera minimal live iso to the
> cd drive and booted from that. the btrfs-tools weren't there, but apt let
> me install them. I gave the btrfs check --repair a shot and lo ...
> success! repairs were made and the server has been up for a few days.
> This is a major improvement from just 3 years ago.
>
> I know, I know, I'm a glutton for punishment for using btrfs, but the
> features are worth it. It really reminds of a couple of previous
> filesystems from the old days, reiserfs and IBM's hpfs from OS/2. It has
> the features of both (b-tree, extent based, dynamic inodes) and then some,
> copy on write and striping of drives together. It says not to run raid 5
> or raid 10, but research shows that the problems that creep up with that
> are due to trying to run raid 5 or 10 with non identical drives (varying
> sizes, etc.). I never do that.
>
> Anyway, I just wanted to relay the story.
>
> Cheers,
> Curtis
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--
Bruce Perens K6BP