There's a lot of moving parts with repairs and how long it takes depends on various factors including (but not limited to):
- how busy the nodes are - how fast the CPUs are - how fast the disks are - how much network bandwidth is available - how much data needs to be repaired It's more art than science trying to predict it but you get closer to science the more successful runs you've had meaning you make an educated guesstimate based on the previous repair runs. The very first run is always pretty bad and consider it an outlier but use the next successive runs as indicators and you should be able to extrapolate from there. Finally, be careful when comparing runs during low traffic periods of the month and primetime/peak. Repairs will run faster when the cluster is not busy and will perform horrendously at peak times since it's competing for the same resources as normal app traffic. Cheers!
