Comment # 6 on bug 1226415 from Stefan Seyfried

No.
The config is: extra partiton for /var/log/journal, to not interfere with the
rest of the system and not be interfered by e.g. "full root fs" causing loss of
journal data.

server:~ # df -m /var/log/journal/
Filesystem                             1M-blocks  Used Available Use% Mounted
on
/dev/mapper/m2--256g-var--log--journal      8182   895      7288  11%
/var/log/journal

The "SystemKeepFree=10%" was actually an invalid config but that one just got
ignored.
"SystemMaxUse" is totally enough to make that work. See the longterm statistics
diagram attached to this bug.

I'm pretty sure what happened was:

* systemd got updated
  * journald.conf got removed, preserved as journald.conf.rpmsave
  * journald got restarted in systemd's %post
  * no custom journald.conf => defaults are used.
    >>>> DATA LOSS HAPPENS HERE <<<
    because the defaults are so that max 10% of the filesystem is used...
    ...80% of the old logs were destroyed.
  * journald.conf.rpmsave is renamed to journald.conf in %posttrans
    => this is way too late, data is lost.

This is extracted from my typescript created during update:

( 152/1152) Installing: systemd-devel-254.10-150600.2.3.x86_64
...........[done]
/usr/lib/tmpfiles.d/systemd-suse.conf:10: Duplicate line for path "/run/lock",
ignoring.
after-local.service is no more provided by systemd but a copy has been
installed in /etc
warning: /etc/systemd/logind.conf saved as /etc/systemd/logind.conf.rpmsave
warning: /etc/systemd/journald.conf saved as /etc/systemd/journald.conf.rpmsave
Failed to try-restart systemd-timesyncd.service: Unit systemd-timesyncd.service
not found.
( 153/1152) Installing: systemd-254.10-150600.2.3.x86_64
.................[done]
...
(1152/1152) Installing: virt-manager-4.1.0-150600.10.1.noarch
............[done]
%posttrans(openssl-1_1-1.1.1w-150600.3.10.x86_64) script output:
mv: cannot stat '/etc/ssl/engines1.1.d.rpmsave/*': No such file or directory
mv: cannot stat '/etc/ssl/engdef1.1.d.rpmsave/*': No such file or directory
%posttrans(systemd-254.10-150600.2.3.x86_64) script output:
Restoring /etc/systemd/journald.conf. Please consider moving your
customizations in a drop-in instead.
For more details, visit https://en.opensuse.org/Systemd#Configuration.
renamed '/etc/systemd/journald.conf.rpmsave' -> '/etc/systemd/journald.conf'
Restoring /etc/systemd/logind.conf. Please consider moving your customizations
in a drop-in instead.
For more details, visit https://en.opensuse.org/Systemd#Configuration.
renamed '/etc/systemd/logind.conf.rpmsave' -> '/etc/systemd/logind.conf'
%posttrans(udev-254.10-150600.2.3.x86_64) script output:
...

systemd-journald gets try-restarted in %postun, so this cannot even be fixed in
the new package, as it is done by the old package already... 

You probably should refuse to update the package completely if the config has
been changed from the default with the warning about "You need to move your
customizations to  a drop-in"