Disk-Space on Ivan Luminaria

Binary logs in MySQL: what they are, how to manage them, and when you can delete them

Tue, 31 Mar 2026 08:03:00 +0100

The message in the infrastructure team’s Slack channel was the kind that makes you look up from your screen: “Disk at 95% on the production db. Anyone able to look?”

The server was a MySQL 8.0 on Rocky Linux, a business management system used by about a hundred users. The database itself was around 40 GB — nothing extraordinary. But in the data directory there were 180 GB of binary logs. Six months’ worth of binlogs that nobody had ever thought to manage.

Full disk on a MySQL cluster: binary logs, Group Replication, and a migration that leaves no room for mistakes

Tue, 14 Oct 2025 08:03:00 +0100

The alert came on a Monday morning, wedged between three meetings and a coffee that was still hot. “Filesystem /mysql at 85% on the primary node.” On another node it was 66%, on the third 25%. In a cluster, when the numbers don’t match across nodes, there’s always something going on underneath.

The first question that comes to mind is “how much space do we need?” But that’s the wrong question. The right one is: “why is it filling up?”