All,
As a long time user of Fedora I have run into nearly all the same issues as mentioned below by Antti.
btrfs is not ready to be default:
On Sun, Jun 28, 2020 at 5:21 AM Antti <antti.aspinen@xxxxxxxxx> wrote:
Hello,
I'm in total opposition to this proposal as a long-time Fedora user. The btrfs is unstable and not ready for production. Most of what I'm about to write is admittedly anecdotal but it's the only file system in Linux which has actively and regularly caused me to lose data on desktops, laptops, servers and even on mobile phones when I haven't taken precautions and done regular backups. Something I don't have to actively do when using ext4 in my workstations and notebooks.
This has happened to me because OpenSUSE and Jolla's Sailfish OS use btrfs as their default file system. I've tried using btrfs from time to time in various environments to see how it's progressing. However there hasn't been fixes for long-standing issues in btrfs when it comes to desktops and laptops in years. Btrfs can still for example run out of its automatically manager "metadata space" which it cannot recover from. Even the relatively recent improvement in kernel 5.8 have already been proven to not improve the situation much although at least the subvolume deletion failing over lack of disk space is now handled slightly better.
You could probably just ask the issue statistics from OpenSUSE and SUSE to see how unreliable btrfs is in reality. I hypothesise that a large majority of OpenSUSE users don't actually use the supposed default file system of their the distro and instead opt to use zfs, xfs and ext4.
I'm honestly in shock that this is even a discussion right now again. If there is a legitimate urgent need to switch the default file system for desktop and laptop users (and I understand why there is pressure to do so since ext4 has a number of shortcomings), then whatever legal obstacles there are blocking the use of zfs should be cleared and zfs should be used instead. Canonical with their Ubuntu is already trying to do this through use of OpenZFS. The xfs has started to have issues as of late but even it would be a legitimate choice.
The absolute first issue with btrfs in desktops and laptops is that it requires active conscious maintenance from the end-users to avoid large number of potentially disastrous situations as well as unconscious regular automatic constant maintenance on background which consume the disks and eat resources. Based on my experiences btrfs works best when you don't use the features you supposedly install it for. It's snapshots are a great example of that. Which is why I suspect that most btrfs "success stories" are ones where the users don't take advantage of the btrfs' features or have actively turned them off conscious of issues they bring up later on. Using btrfs doesn't make using PC easier and instead does the opposite by adding more work. Meanwhile zfs has reliable and working snapshots feature which is in actual use.
With btrfs the following is a very common situation: It's not too uncommon for users to have their entire disks full or near full. Okey, users will then delete some files, maybe few large applications, but in btrfs that is often not enough. User has to manually then run btrfs-balance operation with filters and it usually resolves the situation but it will start happening more frequently until it's completely unsolvable for the end-user without major external assistance or them performing a reformat.
And what inevitably happens with btrfs root volume is that the system can and will stop booting after period of "strange behaviour". Sometimes it can be resolved in maintenance mode but usually the end-user then has to boot a live environment, chroot their system, and clear all hopefully backup'd large files if the system is not in read-only (or clear that obstacle first), clear (most) snapshots, run btrfs-balance operation and do it very carefully or the entire file system might be lost. This will take a very long-time (ranging from 30 minutes to some hours and up to 3-4 days based on my experiences) even on a relatively small SSDs (not to mention HDDs) and it also will shorten SSD lifespan.
If laptop is put into sleep mode without users noticing that btrfs is running maintenance ops on background (and it often is), the likelihood that file system will get corrupt goes up the roof. Something users can do is use TLP and as a first aid set SATA_LINKPWR_ON_BAT=max_performance for TLP which then will shorten the amount of time laptop can be used without recharging. And this has been a standing issue at least since 2015 with no real fix on sight other than "lol, stop using btrfs" like one commentator at Reddit wrote.
The btrfs-check is also a massive can of worms and it cannot be safely run. At least not without reading pages upon pages of manual and becoming an expert in understanding how btrfs works. Expecting every Fedora end-user to do this is unrealistic in many different ways.
The btrfs has no native encryption to my knowledge. However alternatives such as zfs already has a trusted and reliable encryption used in numerous FreeNAS installations around the world.
And much of these issues and many more are straight up mentioned in btrfs' own wiki pages at kernel.org where one of the most shocking admissions is: "So, in general, it is impossible to give an accurate estimate of the amount of free space on any btrfs filesystem. Yes, this sucks."
Source:
https://btrfs.wiki.kernel.org/index.php/FAQ#Why_is_free_space_so_complicated.3F
And these are the brains before btrfs admitting this that there is no solution for this. No amount of userspace tools developmen and UX/DE integration is going to solve this for the end-users.
Please, don't switch to btrfs. It is not mature. It is not well-understood. It is not properly "battle-tested". It can still die on its own. It's just a ridiculous meme file system. At this point it would take me some decade of smooth sailing at OpenSUSE side to start believing that btrfs is ready for prime time in my own personal Fedora systems. Even 5 years of smooth sailing would give more faith in it. But as it stands I have to strongly oppose btrfs. It's too much of a headache with no relief in-sight.
--
Antti (Hopeakoski)
P.S. Sorry for this emotional nature of this message. But I really, really like my Fedora and I really, really dislike btrfs due past highly negative experiences with it (some of them happening to me as recently as last year).
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