What happened:
- Detected SSD in an unmounted state. This particular SSD contained PP-related data, so was non-critical.
- In an attempt to repair without any downtime, I force-unmounted this drive.
- This caused MySQL to crash.
- When MySQL crashes, tables of the MyISAM engine require a fair amount of time to recover.
- I have migrated most of osu! away from MyISAM, but a few key tables remain (due to the sheer performance that can be achieved with this engine).