systemd-journald writes 49KB+ per log line on ext4, 110KB+ on btrfs
Single log line is 49KB+ (ext4) / 110KB+ (btrfs) of systemd-journald disk writes
A GitHub issue reports that systemd-journald causes excessive disk I/O, with a single log line triggering 49KB+ of writes on ext4 and 110KB+ on btrfs. The reporter demonstrates that even at just two log lines per second, a VM sustains ~50 IOPS, far exceeding syslog's efficiency. They argue the journal format is extremely inefficient, and the issue references a previously closed duplicate (#15292). Other users confirm similar problems, with one seeing nearly 7GB written in 15 minutes and another providing detailed measurements showing 752 bytes of actual data resulting in over 200KB of writes.
Journald just uses extremely inefficient format (also I've seen it corrupt on unclean reboot enough times to declare it's not even all that resilient) as files are also multiple times the size of what's actually written in them.