Subject: Re: [bug#45692] [PATCH 0/3] Better Support for ZFS on Guix

From: Maxim Cournoyer <[email-masked]>
Date: Sun, 20 Mar 2022 00:42:59 -0400

Hi,

raid5atemyhomework via Guix-patches via <[email-masked]> writes:

> Hello Maxime,
>
>>     -   That seems rather inconvenient, why not use BTRFS instead which
>>         seems quite capable and doesn't have this weird restriction?
>
> BTRFS IS NOT CAPABLE.
>
> Did you notice my pseudonym?  "`raid5` ate my homework".  I used the
> BTRFS `raid5` mode, once.  It LOST MY DATA.  Never again.  ZFS
> supports RAIDZ1 and has not lost my data at all yet.  I've replaced
> ZFS disks on my pool.  No data loss.  It keeps on going on.
>
> A file system that loses data is not a file system.  It is a disaster.
>
>
> BTRFS is not an acceptable substitute for ZFS.
>
> If ZFS is removed from Guix, I am switching to Ubuntu and keeping my
> ZFS pool, I am not going to switch to BTRFS just to keep running Guix,
> I would *like* to run only fully-free software, especially since I
> took the trouble of paying a premium for a server that had coreboot,
> but my data is more important and BTRFS is not an acceptable
> substitute for ZFS.

Btrfs RAID5 or RAID6 having a write hole leading to potential data loss
upon hard reset has been a known issue for like a decade, and nobody has
worked on improving that [0].  RAID10 is fine though, and so is RAID1 or
RAID0.  I've used it (Btrfs RAID1 with zstd compression) for years on
various Guix systems without any issue.

> The only restriction needed is to prevent binary redistribution.  Yes,
> I agree it is inconvenient to always have to transfer source code and
> recompile each time.  But it is a ***lot*** more inconvenient to
> replace my lost data because BTRFS couldn't cut it despite more than a
> decade of development.  At least I can re-download the source code for
> ZFS each time from many trivial sources.  My `/home`, I cannot.  That
> is a bigger inconvenience.

With my personal experience suggesting that Btrfs is a solid file
system, I respectfully disagree :-).  At any rate, don't forget to
backup your precious data to somewhere safe; as RAID is no substitute
(ever had a PSU failure blowing up multiple components?).

Thanks,

Maxim

[0]  https://btrfs.wiki.kernel.org/index.php/Status#RAID56