Comparing two Ceph CRUSH maps
Sometimes you want to test if changes you are about to make to a CRUSH map will cause data to move or not. In this case I wanted to change a rule in CRUSH where it would use device classes, but I didn’t want any of the ~1PB of data in that cluster to move. […]
Safely backing up your Ceph monitors
So you might wonder: Why do I need to make a backup of my Ceph monitors? I have multiple monitors. That’s true, but would you run into the very unfortunate situation where you loose all you monitors, you loose all your data. The monitors contain very important metadata (pgmap, osdmap, crushmap) to run your cluster. […]