Today when I tried to perform some MySQL tasks and got error 28. After several searches I found that this error means that no free space is left on server HDD. When I ran df command, I was very surprised, but my disk usage was 100% – so much that MySQL couldn’t even create a log file. It’s a strange thing I didn’t notice this before. I had to check MySQL when my blog’s categories have disappeared. I highly recommend to enable DirectAdmin disk usage warning as I eventually missed disk overuse on my VPS.