Re: btrfs recommended layout for snapshots?

[Maxim Cournoyer]

Hi,

Felix Lechner via "Development of GNU Guix and the GNU System
distribution." <guix-devel@gnu.org> writes:

> Hi Nicolas,
>
> On Mon, Aug 14, 2023 at 7:06 AM Nicolas Graves via Development of GNU
> Guix and the GNU System distribution. <guix-devel@gnu.org> wrote:
>>
>> not snapshotting the rootfs
>>   This would allow to simply care about only a few "user data"
>>   directories
>
>> I .. would be glad to find one
>
> I believe Guix does a good job of managing system generations and only
> snapshot user data. (My root is also on a faster ext4 file system, not
> Btrfs.) Here is what I do. [1]

I agree, unless you very high requirements to minimize downtime in case
of failures, thus justifying the need of snapshotting the root fs and
backing it up to external storage, just snapshotting /home should be
good enough for most users.

I'd still opt for a flat subvolume layout to preserve the ability to
snapshot / at all in the future, in case you ever need to.  That's
tentatively covered/explained in info '(guix)Btrfs file system'.

> In order to avoid confusion with the live file system, I mount
> snapshots volumes separately under /history. [2] My user data is
> generally also encrypted and mounted to /home from networked folders
> under /acct.

Do note that you may run out of inodes if your store grows very large.
zstd compression also helps a lot ot keep /gnu/store growth in check,
and should reduce wear to flash based storage.

-- 
Thanks,
Maxim