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Re: BTRFS snapshot space consumption (was: New laptop: need advice on choice...)




Felix Miata <mrmazda@xxxxxxxxxxxxx> writes:

> Anders Andersson composed on 2019-04-13 17:31 (UTC+0200):
>
>> Felix Miata wrote:
>
>>> Because of its snapshotting, BTRFS requires considerably more space than older
>>> filesystems, as much as double.
>
>> A btrfs snapshot takes approximately zero space. Where did you get
>> this idea from? 
>
> 1: "Disk Space Full Because of Snapper" on https://en.opensuse.org/SDB:BTRFS

i only skimmed that, good resource for anyone even not on SUSE.

> 2: Since 2015, BTRFS has been the default / filesystem on openSUSE, which
> recommends minimum / filesystem size of 20GB for EXT4, compared to 40GB for BTRFS.

>From my experience I think they only use snapshotting on BTRFS volumes,
I don't know if they support it with LVM, but is it even possible with
ext4 only?

And yeah, no surprise, if you want snapshots, you'll need more capacity,
it would probably the same recommendation with LVM

And the effects of using snapshots is assuring, you simply set the
system to auto-update everything, and if your system doesn't boot, you
simply select the older snapshot from the grub menu and have your system
running in no time. (This was my scenario with a SUSE desktop, I tried
tumbleweed aka SUSEs unstable/experimental distribution, where some
instability was expected)

I would never recommend something like that for server updates/upgrades,
as there a other far more procedures you can follow to test verify and
prevent service loss on failed updates, if you simply cluster your
services.

I would be pissed if my OS removes snapshots I might or might not need
in the future.  That's a release critical bug in my eyes.  Yeah, I know
Microsoft and Apple do that automatically if your capacity runs out, but
that's also why I don't recommend them at all.

Have a monitoring on all your systems, track each and every possible
value in compact rrd databases, calculate trends from those values and
you'll never be surprised by filled up disks, growing defects detected
by SMART etc.

I'd like a debian desktop/notebook/tablet where snapshots were
implemented in a openSUSE manner, so that I can simply forget about
updates, have them installed in background und can go to the snapshot if
problems arise.

Peter