Mysql 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.

Galera Cluster with 3 nodes: how I solved a MySQL availability problem

Tue, 17 Feb 2026 08:03:00 +0100

The ticket was laconic, as it often is when the problem is serious: “The database went down again. The application is stopped. Third time in two months.”

The client had a MariaDB on a single Linux server — a business management application used by about two hundred internal users, with load spikes during end-of-month accounting closures. Every time the server had a problem — a disk slowing down, a system update requiring a reboot, a process consuming all the RAM — the database crashed and with it the entire business operations.

MySQL Users: Why 'mario' and 'mario'@'localhost' Are Not the Same Person

Tue, 13 Jan 2026 08:03:00 +0100

A few weeks ago a client calls me. Pragmatic tone, seemingly trivial request:

“I need to create a user on MySQL for an application that needs to access a database. Can you take care of it?”

Sure. CREATE USER, `GRANT` , next.

MySQL Multi-Instance: A Ticket, a CSV and the secure-file-priv Wall

Tue, 04 Nov 2025 08:03:00 +0100

The ticket said: “We need a CSV export from the orders table in the ERP database. By 2 PM.”

It was 11 AM. Three hours for a SELECT with INTO OUTFILE — a five-minute job, I thought. Then I opened the VPN, connected to the server and realized five minutes were not going to cut it.

The server was a CentOS 7 box running four MySQL instances. Four. On the same host, with four different systemd services, four different ports, four different Unix sockets, four different data directories. A setup someone had put together years earlier — probably to save on a second server — and that no one had touched or documented since.

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?”